Glossary

Every term, in one place

The same 186 definitions the lessons link to inline, wherever a sentence uses them — gathered here so a definition is never more than one page away.

A

absolute phraseabsolute phrases: A noun followed by a modifier — often a participle, sometimes just an adjective — that describes the whole clause it's attached to rather than any single noun inside it: "the stitching barely visible, the quilts reveal themselves up close." It has no verb tying it to a subject of its own, so it can never stand alone as a clause and never takes a semicolon or period in front of it.
ac methodfactoring by grouping: The technique for factoring a trinomial ax² + bx + c when a ≠ 1: multiply a by c, find a pair of numbers with that product and a sum of b, split the middle term into those two pieces, then factor by grouping.
adaptivemultistage adaptive, adaptive engine, adaptively: The digital SAT gives everyone the same first module in a section, then routes you to an easier or harder second module based on how the first went. Reading & Writing and Math route independently, so a strong Math module 1 does not affect which Reading module you get.
agreement attraction: A documented error pattern in fluent speech: a nearby plural noun pulls a verb or pronoun into agreeing with it even when it isn't the subject. It's why long interrupters between a subject and its verb are the SAT's favorite trap, and why reading a sentence aloud can't catch the error.
altitudealtitude-matching, sort on altitude: How broad or narrow a statement's scope is relative to what a passage actually supports — a detail sits too low, an inflated generalization sits too high, and the credited answer matches the passage's own altitude exactly.
annulusannular, annular region: The ring-shaped region between two concentric circles — a washer's or pipe's cross-section — with area π(R² − r²), the big circle's area minus the small one's.
antecedent: The noun a pronoun refers back to. A pronoun must match it in number — a rule the test breaks most often by putting a plural noun near a singular antecedent to make the wrong choice sound right.
appositiveappositives, comma-fenced appositive: A noun phrase set off by commas that renames the noun next to it — "Farouk El-Baz, a geologist and space scientist,". It describes one thing rather than adding a second subject, so it never turns a singular subject plural.
arcarcs, arc length, arc measure: A piece of a circle's rim between two points. Its MEASURE (in degrees or radians) is just the central angle that cuts it off and doesn't depend on the circle's size; its LENGTH is a distance that does.
aspectverb aspect: Whether a verb describes something finished, ongoing, or still relevant now, layered on top of its tense — simple, progressive, and perfect are the three the SAT tests. Two sentences can share a tense and still need different aspects.
audience clause: The part of a goal naming who the sentence is written for — "to an audience already familiar with X" or "unfamiliar with X." It decides whether X may be assumed as known or must be explained inside the credited sentence.

B

back-substitutionback-substitute, back-substituting: After solving for one variable, plugging that value into an equation to find the second variable — the second half of solving a system by substitution or elimination.
base (of a percent)the base, percent base: The quantity a percent is measured against — the number that follows "of" or "than," treated as 100%. Nearly every wrong answer on the percentages skill comes from dividing or multiplying by the wrong base rather than from bad arithmetic.
blocked practiceblocking, blocked: Practising one problem type repeatedly before moving on. The right way to learn a procedure for the first time, and the wrong way to keep practising it — once you can execute it, blocking lets you run on autopilot without ever practising recognition.
Bluebook: College Board's own testing app — the software you sit the real exam in, and the only place to take official adaptive practice tests. Practising in it matters because memory is sensitive to how closely practice matches the real conditions.
boundary (of an inequality)boundary line, boundary point: The line (in two variables) or point (in one variable) obtained by replacing an inequality's symbol with =. Solid or filled when the symbol is inclusive (≤, ≥), dashed or open when strict (<, >) — the boundary itself is a solution only in the inclusive case.
box plotbox plots, box-and-whisker plot: A plot of a data set's five-number summary — minimum, Q1, median, Q3, maximum — as a box with whiskers. It shows no mean, no mode and no sample size, and each of its four sections holds about a quarter of the data regardless of how wide that section is drawn.
bridging inferencebridging inferences: The connection a reader's mind supplies automatically between two sentences that arrive with no explicit link — the mechanism that makes ordinary prose readable, and the same mechanism that makes a wrong transition word feel right once it's been dropped into the blank.

C

careless errorcareless errors, slip, slips: A miss on a question you demonstrably know how to do — a sign dropped, a unit ignored, the right answer to the wrong question. At the top of the score range these are the majority of remaining points, and they respond to process changes rather than more content study.
central angle and inscribed anglecentral angle, inscribed angle: A CENTRAL angle has its vertex at the circle's centre and equals the arc it cuts off exactly; an INSCRIBED angle has its vertex on the circle and equals exactly half that arc. Confusing which one a figure shows is the single most common circle-angle error.
chordchords: A segment joining two points on a circle; a diameter is the longest possible chord. The perpendicular from the centre to a chord always bisects it, which is what turns most chord-length items into a right triangle.
claimclaims: What a text asserts about its topic — a full sentence with a position in it that a reasonable person could contradict — as opposed to what the text is merely about, its topic. The claim/topic distinction underlies nearly every Reading & Writing item type, not just cross-text pairs.
claim and evidence: A CLAIM is something a text asserts as true; EVIDENCE is what the text offers in support of a claim. A text can present evidence for a claim without endorsing it, which is why "presents evidence for" and "asserts" are different — and separately correct or incorrect — answers to the same question.
coefficientcoefficients: The number multiplying a variable. In 3x + 7, the coefficient of x is 3. In a real-world equation the coefficient is almost always the rate, and the lone number is almost always the starting value.
comma splice: Two independent clauses joined with only a comma. Always wrong on the SAT. The fixes are a period, a semicolon, a comma plus a coordinating conjunction, or making one clause dependent.
comparison groupcontrol group: The group in an experiment that does not receive the treatment being tested, or receives a different one. Without one, there is nothing to attribute a change in outcome to — even with a perfectly random sample and perfect measurement.
complementcomplements, subject complement: The word or phrase that completes a linking verb by describing or renaming the subject, rather than receiving an action the way an object does — "exhausted" in "The engineer seemed exhausted," "Ana" in "The winner was Ana." A linking verb is not a complete predicate on its own; delete the complement and "The winner was" is a fragment.
complement (probability)complement rule, 1 minus P: P(not A) = 1 − P(A). It has to be computed inside whatever population a condition has already narrowed to — taken over the wrong pool, the result isn't the complement of anything actually asked for.
complementary anglescomplementary: Two angles whose measures sum to 90°. It only belongs in a figure where a right angle is genuinely present — reaching for it where the figure calls for supplementary (180°) is one of the most common silent errors in geometry.
completing the squarecomplete the square: A procedure for rewriting a quadratic ax² + bx + c into vertex form a(x−h)² + k by folding part of the expression into a perfect square. Always works, even when the quadratic doesn't factor over the integers.
compound inequalitycompound inequalities: An inequality with a variable expression trapped between two bounds, written as a < x < b or a ≤ x ≤ b. Solved by applying the same operation to all three parts at once; dividing all three parts by a negative reverses both symbols and swaps which bound is which.
concede / qualify / complicate / refute: The four things a sentence can do to a prior claim, and the test distinguishes all four: CONCEDE grants the claim, usually right before turning against it; QUALIFY keeps the claim but narrows its range; COMPLICATE introduces something the claim doesn't handle without calling it false; REFUTE asserts the claim is wrong. The hardest function and structure items often turn on which of the four a given sentence is doing.
concessionconceded material, concessive clause: Material a goal or a sentence grants before making its real point, signaled by "despite," "although," or "even though." Conceded material must appear and must sit in a subordinate position — putting it in the main clause reverses the sentence's emphasis.
conditional probability: The probability of one thing given that another is already true. In a two-way table, the entire skill is choosing the right denominator: 'given' tells you which row or column you're now confined to.
confidence interval: The range an estimate is reported within, at a stated confidence level. Widening the interval is what buying more confidence costs you, which is why a 99% interval is always wider than a 95% one from the same data.
confoundconfounding, confounding variable, confounds: A factor other than the one being tested that could independently produce the same result. It's the standard target of the strongest weakener on a causal-conclusion item, because ruling it out — not contradicting the data — is what actually breaks a causal claim.
congruent trianglescongruent, congruence: Triangles with every corresponding side and angle equal — similar with a scale factor of exactly 1. Proven by SSS, SAS, ASA, AAS, or HL; never by SSA or AAA.
conjugate: The expression formed by flipping the sign between two terms — the conjugate of a + b is a − b. Multiplying a fraction by conjugate-over-conjugate is a standard way to rationalize a denominator without changing the fraction's value.
conjunctive adverbconjunctive adverbs: A word like "however," "therefore," or "moreover" that signals a logical relationship between two clauses but, unlike a FANBOYS conjunction, has no power to join them — a comma in front of one at a clause boundary is still a comma splice.
connectiveconnectives, signal word, connective word, transition word, transition words: A word or phrase — "however," "therefore," "in other words," "for example" — that states the logical relationship between what comes before it and what comes after: a consequence, a contrast, an illustration, a restatement. On Transitions it's the actual answer, not vocabulary to recognize; on Words in Context and Inferences, reading it first is step one of predicting what a blank or credited choice needs to say.
constant (math)constant, constant term: The lone number in an equation that isn't multiplying the variable — the +7 in 8x + 7 = 83 — as distinct from the coefficient, which does multiply it.
content echo: The most frequently chosen wrong answer on function items: a choice that accurately restates what a sentence says rather than naming the job it does for the surrounding argument. Test for it by asking whether the choice could have been written by someone who read only the underlined sentence and nothing around it — if so, it's a paraphrase, not a function.
contextual domaindomain restriction: The restriction a real-world model puts on its own valid input range — a draining tank's model going negative past empty, or a headcount that must land on a whole number. The model's algebra doesn't know about the restriction; only the context does.
correlative conjunctioncorrelative pair, correlatives: A conjunction that works as a matched pair — not only...but also, either...or, neither...nor, both...and. Whatever grammatical unit follows the first half must be matched by the same kind of unit after the second.
corresponding anglescorresponding angle: The angle pairs that sit in matching positions at each of the two crossings a transversal makes with two lines. Equal exactly when the two lines are parallel — the fact the converse-parallel-lines proof rests on.
coterminalcoterminal angles: Two angles that land on the same ray after any number of full rotations, differing by a multiple of 360° (or 2π radians). An angle like 565π/6 is solved by stripping off full turns until a familiar angle between 0 and 2π is left.
cross-multiplycross-multiplication, cross-multiplying: The shortcut for solving a proportion — a/b = c/d becomes ad = bc — which is safe only once the same quantity has been confirmed to sit in the same position on both sides of the equation.

D

degenerate casedegenerate cases, degenerate solution, degenerate system: One of the two non-generic outcomes for a linear equation or system — no solution, or infinitely many solutions — as distinct from the ordinary single-answer outcome. For a system, it happens when the two equations describe the same line or two parallel lines rather than crossing exactly once.
degenerate circledegenerate radius: What (x − h)² + (y − k)² = r² describes when r² isn't positive: a single point if r² = 0, and no graph at all if r² is negative. The SAT uses this as a genuine correct answer, not just an edge case to ignore.
dependent clausedependent clauses, subordinate clause: A clause with a subject and a verb that cannot stand alone, because a word like 'because', 'although' or 'which' makes it lean on something else. Joining one to an independent clause needs no semicolon, which is why spotting it settles most punctuation questions.
desirable difficultydesirable difficulties: A change to practice that makes it feel harder and go worse in the moment, while producing better retention later. Spacing and interleaving are the two big ones. The defining property is that you will dislike them and they will work, which is why satisfaction cannot be allowed to drive a study schedule.
Desmos: The graphing calculator built into Bluebook, available on every Math question. Many questions that look like algebra are faster solved by graphing both sides and reading the intersection. Practise on the restricted testing build, desmos.com/testing/cb-digital-sat/graphing — the full consumer desmos.com app has extra features Bluebook disables, so drilling only on the consumer app risks leaning on a feature that isn't there on test day.
difference of squares: The factoring pattern a² − b² = (a − b)(a + b). Applies only to a subtraction of two squared terms; a sum of squares, a² + b², has no such pattern over the real numbers.
dilationdilated, dilations: A transformation that scales every distance from a fixed center by the same factor. It preserves every angle measure exactly, regardless of the scale factor — only lengths change.
dimensional analysisunit analysis, factor-label method: Treating units as algebraic symbols that multiply and cancel like variables, so that chaining conversion fractions and watching which units survive both performs a conversion and checks it in the same step.
discriminant: The b² − 4ac inside the quadratic formula. Its sign alone tells you how many real solutions a quadratic has: positive means two, zero means exactly one, negative means none — which is often the whole question.
distractordistractors, wrong choice, wrong choices: An incorrect answer choice. Good ones are not random — each is the answer you'd reach by making one specific, plausible mistake, which is why the wrong choice you picked tells you more than the right one.
domain (algebra)domain: The set of input values for which an expression or function is defined. Distinct from "domain weight" (a College Board content-area percentage) — the two senses of the word sit close together in test-prep explanations and are easy to conflate.
domain weightdomain weights: The published percentage of a section's score that one of its content domains contributes — College Board states Information and Ideas is about 26% of Reading & Writing, for instance. It's the only officially published breakdown; the split among the individual skills inside a domain is not published, and any specific figure for one is a prep-industry estimate.
double rootdouble roots, repeated root: A solution where the quadratic factors as a perfect square, so the two roots the quadratic formula would normally produce collapse into the same value — the discriminant is zero, and the parabola touches the x-axis at its vertex instead of crossing it twice.

E

eliminationeliminate, elimination method: Solving a system by scaling one or both equations until a variable's coefficients match or are opposite, then adding or subtracting so that variable drops out, leaving one equation in one variable.
entailmententailed, entails: A conclusion that must be true given the stated premises, as opposed to one that is merely probable or plausible given them. The standard an Inferences completion is held to: not "is this a reasonable thing to conclude" but "could this be false while every given sentence stays true."
error log: A record of every question you got wrong and, more importantly, why — content gap, misread, careless slip, or timing. Sorting misses by cause is what separates the students who improve from the students who keep taking practice tests.
excluded valueexcluded values: A number that would make a denominator zero — ruled out of an expression's domain (the value behind a phrase like "for all x ≠ 3") and, in a rational equation, disqualified as a solution even if it satisfies the polynomial produced after the fractions are cleared.
extraneous solutionextraneous solutions, extraneous: A value that appears when you solve an equation but doesn't actually satisfy the original — a standard side effect of squaring both sides or clearing a denominator. Radical and rational equations require checking every answer back in the original equation.

F

FANBOYSFANBOYS conjunction, coordinating conjunction, coordinating conjunctions: The seven words that can join two independent clauses after a comma: for, and, nor, but, or, yet, so. The list is closed — no other word licenses a comma at a clause boundary, and a look-alike such as "however" is an adverb, not one of these.
five-number summary: Minimum, first quartile, median, third quartile, maximum — the five values a box plot displays. Two very different data sets can share one exactly.
fluency trapfluency illusion, illusion of competence: Re-reading and highlighting make material feel familiar, and familiarity feels like knowing. It isn't. Both rate poorly as study methods precisely because the confidence they produce ends study early — you stop before you can actually retrieve anything.
format fidelitytransfer-appropriate processing: How well you remember something depends on how closely the way you practised matches the way you'll be tested. Free-recall flashcards build a different skill from four-option multiple choice under time pressure — so practice for a multiple-choice test should be multiple choice, timed, on a screen.
frequency table (one-variable)frequency distribution: A table pairing each distinct value in a one-variable data set with how many times it occurs. To find the mean, weight each value by its frequency and divide by the total frequency, not by the number of rows; to find the median, walk the cumulative count rather than sorting.
function: What one sentence or clause does for the argument around it, as opposed to what it says. Answered by reading the sentence immediately before and after it and naming the relationship — "it concedes X so that Y can land" — not by paraphrasing the sentence's content.
function (math)f(x) notation, function notation: The notation f(x), read "f of x," for a rule that takes one input and returns exactly one output — f(3) means the output when x = 3, not f multiplied by 3. A different sense from the Reading & Writing "function" elsewhere in this glossary, which is what a sentence does for a passage's argument.
function transformationtransformation of a function: The rules for how a formula change reshapes a graph: f(x) + k shifts it up k, f(x + k) shifts it left k, k·f(x) stretches it vertically by k, and f(kx) compresses it horizontally by a factor of k. Outside changes act on the output and behave as expected; inside changes act on the input and behave backwards.
furniture (of a figure)figure furniture: The non-data parts of a graph or table that establish what its numbers mean before a single value is read: title, axis labels, units, scale, and legend.
fused sentencerun-on sentence, run-on: Two independent clauses pushed together with no punctuation and no conjunction between them — the more extreme sibling of a comma splice, and equally wrong on the SAT.

G

gerundgerund phrase, gerunds: An -ing verb form used as a noun — "Reconciling the two data sets requires...". A gerund phrase acting as a subject is always singular, no matter how many plural nouns it contains.
goal sentencegoal, the goal: On a Rhetorical Synthesis item, the single sentence naming the act a credited choice must perform on the notes — emphasize, compare, introduce, explain why. It's a requirement list, not scene-setting, and every clause in it constrains which choice is correct.
grid-ingrid-ins, SPR, student-produced response: A Math question with no answer choices — you type the answer yourself. About a quarter of Math questions. There is no penalty for a wrong one, and the entry format has its own rules about fractions, decimals and negative signs.

H

half-planeshaded region, solution region: The solution set of a linear inequality in two variables: one of the two regions a boundary line divides the coordinate plane into.
half-righthalf right, partially correct: A choice whose first half is exactly right and whose second half is wrong. It is the most dangerous distractor family because recognising the correct opening is enough to stop reading — the fix is to read every choice to its final word.
hedgehedging, hedged, modality, hedge matching, hedged claim: Modal or qualifying language — "may," "suggests," "some argue," "does not by itself establish" — that limits how strongly a claim is being made, as opposed to an unhedged word like "proves" or "confirms." Matching a passage's hedge to an answer choice's strength, not just its direction, is what the credited choice does across Reading skills, where an unhedged rewrite of a hedged claim is the standard trap.
helping verbhelping verbs, auxiliary verb, auxiliary verbs: A verb that attaches to a main verb to build a tense, a question, or a passive form, rather than carrying the sentence's meaning on its own — is, was, has, have, had, do, does, did, will, can, could, should. "Was" in "was boiling" and "had" in "had eaten" are helping verbs; the meaning lives in "boiling" and "eaten," but it takes the pair together to make a verb the sentence can actually use. An -ing word never counts as a sentence's main verb unless a helping verb like this sits in front of it.
hypercorrectionhypercorrection effect, confidently wrong: Errors you were confident about are corrected more durably than errors you guessed at, once you're told the right answer. It is the reason this course asks how sure you are before showing feedback: a confident miss is the highest-value thing you can find.

I

identity (math)identity, mathematical identity: An equation that's true for every value of the variable, not just some — as opposed to an equation you solve for one specific value. sin²θ + cos²θ = 1 holds for every angle θ; that's what makes it an identity rather than something to solve.
independence (statistical)statistically independent, association (statistics): Two traits are independent when knowing one tells you nothing about the other — in a two-way table, every row's internal split matches the grand total's split. When the splits differ, the traits are associated, though association alone is never evidence of causation.
independent clauseindependent clauses, main clause: A group of words with a subject and a verb that could stand alone as a sentence. Nearly every punctuation rule on the test reduces to how many independent clauses you have and what's joining them.
inscribedinscribed figure, circumscribed: A figure drawn so it fits entirely inside a larger figure, touching it only at specific points — a sphere inscribed in a cube touches all six faces; a cube inscribed in a sphere touches only at its corners.
interleavinginterleaved practice, mixed practice: Mixing problem types within a session instead of doing twenty of one kind in a row. It works by forcing you to identify which kind of problem you're looking at — a step blocked practice skips entirely, and the exact step the real test demands.
interquartile rangeIQR: Q3 minus Q1 — the width of the box in a box plot, and a measure of spread that describes only the middle half of the data while ignoring the outer quarters entirely.
inverse proportioninversely proportional, inverse variation: Two quantities whose product stays constant (xy = k), so one rises exactly as fast as the other falls — more workers, proportionally fewer hours for the same job. Easy to confuse under time pressure with direct proportion (y = kx).

J

joint probability: The probability that a randomly selected member carries two traits at once — one interior cell of a two-way table divided by the grand total, with no condition applied. Distinct from a conditional probability, which divides that same cell by a row or column total instead of the grand total.

L

linearlinear relationship, linear function: A relationship whose rate of change is constant: the same increase in the input always produces the same change in the output. Graphs as a straight line, and is exactly the condition that lets you use slope at all.
linking verblinking verbs: A verb that shows no action and instead connects a subject to a word or phrase that describes or renames it — is, seems, became, remained, feels. In "The eruption was catastrophic," "was" does nothing on its own; it just links "the eruption" to the description "catastrophic," so the word after it describes the subject rather than naming something the subject did to anyone.
load-bearing: A word, symbol, or clause that changes what the correct answer has to do if it's altered or removed — a contrast word in a passage, a strict-versus-inclusive inequality symbol, a squared term in an identity. Spotting which parts of a problem are load-bearing and which are decoration is a skill that transfers across every domain on the test.

M

margin of error: The width of the plausible range around an estimate from a sample. A larger sample narrows it; higher confidence widens it. It describes sampling variability only — it says nothing about whether the sample was biased.
marginal probability: The probability that a randomly selected member has one particular trait, nothing conditioned away — a row or column total divided by the grand total. Distinct from a conditional probability, which narrows the denominator to that row or column first.
masterymastered, mastery threshold: In this course, a skill counts as mastered when your recent attempts at it are consistently correct — not when you have read the lesson. Progress bars here measure that, deliberately, because a bar that fills as you scroll measures reading speed and nothing else.
misconception tagmisconception, named trap, trap: The short label attached to each wrong answer here, naming the reasoning error that produces it. Tagging them turns your wrong answers from a score into a diagnosis — the same tag appearing repeatedly is the thing to fix.
modifiermodifiers, dangling modifier, misplaced modifier: A phrase describing something else in the sentence. It must sit next to what it describes — when it doesn't, the sentence claims something absurd, which is exactly what the question is testing you to notice.
modulemodules, module 1, module 2: One separately timed block of questions. Each section has two: Reading & Writing is 2 × 27 questions in 32 minutes each, Math is 2 × 22 questions in 35 minutes each. You cannot return to module 1 once it ends.

N

negation testnegate the sentence: A check for whether a fact sits in a sentence's main clause or in a modifier: negate the main clause and see whether the fact survives untouched. If it does, the fact was background, not the sentence's assertion, and can't be what the sentence emphasizes.
negative reciprocalnegative reciprocals: Flip a number's fraction and its sign. It's the relationship between the slopes of two perpendicular lines — a slope of 3 has negative reciprocal −1/3.
non-response biasnonresponse bias, self-selection bias: A distortion introduced when who chooses to answer a survey differs systematically from who was sampled — the strongly opinionated reply, the busy or indifferent don't. Invisible to the margin of error, which measures only variability from the random draw itself, not who bothered to respond.
nonresponsenon-response, response rate, attrition: The gap between how many subjects were invited or selected and how many actually took part. When response is voluntary, the participants who remain are a self-selected subset carved out of a random invitation list — no longer the random sample the study started with.
nounnouns: A word that names a person, place, thing, or idea — kettle, Trieste, Hedy Lamarr, happiness. It is the unit every other part of a sentence attaches to or describes, which is why finding the nouns in a sentence tells you what it's about before you've worked out what it says.
noun clausenoun clauses: A clause that functions as a single noun inside a larger sentence — as a subject, an object, or a complement — rather than as a free-standing statement. In "Scientists determined how the mixing varies," "how the mixing varies" is the object of "determined," not an independent clause, which is why no punctuation separates it from the verb that governs it.

O

objectobjects, direct object, direct objects: The noun or pronoun that receives a verb's action, as opposed to the subject, which performs it. In "The committee reviewed the manuscript," "the committee" is the subject doing the reviewing and "the manuscript" is the direct object being reviewed. Pronoun case tracks exactly this split: a pronoun performing the verb takes subjective case (he, she, they), one receiving it takes objective case (him, her, them).
observational studyobservational studies, observational design: A study where the researcher only records what subjects are already doing, with nothing assigned. It can support an association but never a causal conclusion, no matter how large or well-sampled the resulting data is.
orientation-by-cancellationorientation-unchecked: This course's name for choosing which way to flip a conversion fraction — not by a memorized direction rule, but by putting the unit you want gone on the side that cancels it.
outlieroutliers: A value that sits unusually far from the rest of a data set. It moves the mean, the range and the standard deviation, because those are built from every value's size or distance — it generally leaves the median and the mode alone, because those are decided by position and by frequency.
overreach: A wrong answer that says more than the passage supports — right topic, right direction, but a stronger claim than the text actually licenses. Among the most common ways strong readers lose Reading points.

P

parallelismparallel structure, parallel: Items in a list or comparison have to share grammatical form: running, swimming and cycling, not running, swimming and to cycle. Tested most often in long lists where the break is far from the start.
parameterparameters, parameter question, parameter questions, parameter item: A letter standing for a fixed but unknown constant in an equation or system, as opposed to the variable actually being solved for — the k in kx + 3 = 5x + 9 is a parameter, not x. Its value can determine how many solutions a linear equation or system has, which is what a "for what value of k" question is asking.
parameter and statisticpopulation parameter, sample statistic: A parameter is a number describing the whole population (the true mean or proportion, almost never known exactly); a statistic is the same kind of number computed from a sample (always known exactly). Inference is the bridge from the statistic to the parameter.
participial phraseparticipial phrases: A modifying phrase built from an -ing or -ed verb form — "donated by the historian," "having lain under ash" — that describes a noun rather than naming its own action. Like a prepositional phrase, it can never contain the subject it modifies.
percent changepercentage change: (new value − old value) ÷ old value, expressed as a percent. The denominator is always the starting value, regardless of which of the two numbers is larger or which the sentence names first.
percentage pointpercentage points: The unit for the raw arithmetic difference between two values that are themselves percentages — a rate going from 24% to 30% rose 6 percentage points. Distinct from the percent change of that same rate, which divides the gap by the starting percentage; the two numbers are routinely offered as a paired trap in the same answer set.
pivot: The point where a short passage turns, usually marked by a contrast word — "but," "however," "yet" — or an explicit inference-block like "the finding does not show." On purpose and structure items the credited answer almost always lives after the pivot; a choice built only from pre-pivot material describes the setup, not the point.
point estimateestimate, point estimates: The single number — a sample mean or proportion — that sits at the centre of a confidence interval, before the margin of error is applied on either side.
point-biserial correlationpoint-biserial, discrimination (item statistic): A statistic showing whether getting a specific question right predicts doing well on the test overall — the standard discrimination-quality check run on a multiple-choice item after it goes live. Low or negative values flag a broken or mis-keyed item.
point-slope formpoint-slope: The equation y − y₁ = m(x − x₁), built from a known slope m and any one known point (x₁, y₁) — the form to reach for when given a slope and a point that isn't necessarily the y-intercept.
predicatepredicates: Everything a sentence says about its subject — the main verb plus whatever completes or extends it: an object, a complement, a modifier. In "The engineer calculated the load carefully," "the engineer" is the subject and "calculated the load carefully" is the predicate. A clause needs both a subject and a predicate to be complete; a sentence that stops before the predicate finishes is a fragment, however long it has become.
prepositional phrase: A preposition — of, in, on, with, between, during — followed by a noun. The subject of a sentence is never inside one, which is why striking these out is the single most useful move on a subject-verb agreement question.
prequestionprequestions, prequestioned, pretesting: A question asked before the material is taught. Getting it wrong is the mechanism, not a failure — attempting an answer first measurably improves how well the subsequent explanation sticks. The effect applies only to what was prequestioned, which is why these target the highest-value ideas rather than warming you up generally.
pronoun casesubjective case, objective case, case: Which form a pronoun takes based on the job it does in its own clause. Subjective case (who, he, she, they) performs the verb; objective case (whom, him, her, them) receives the action, as a direct object or as the object of a preposition. Settle who/whom by substituting he or him: if he fits, use who; if him fits, use whom.
purposemain purpose: What an author is doing to the reader with a text — always expressible as "to + verb": to report, to concede, to compare, to complicate. Distinct from the main idea, which is a proposition the text asserts; a choice can state the idea perfectly and still fail to name the act.
Pythagorean triplePythagorean triples, triple, triples: A set of three whole numbers satisfying a² + b² = c² exactly — 3-4-5, 5-12-13, 8-15-17, 7-24-25, and every multiple of them. Recognizing one on sight turns a Pythagorean-theorem calculation into an instant lookup instead of a square root.

Q

quantifier inflationquantifier-inflation: A wrong-answer pattern that bolts an absolute — all, none, only, never, always, any, proves, cannot — onto a claim the passage only supports narrowly, turning "in this trial" into "in general." One of the most common named traps on Inferences and Central Ideas items.
quartilequartiles, Q1, Q3, first quartile, third quartile: One of the three values that split a sorted data set into four equal-sized groups — Q1 marks the 25% boundary, the median marks 50%, Q3 marks 75%. A box plot draws all three plus the minimum and maximum.

R

radianradians: The SAT's other unit for angle measure, defined as the angle whose arc equals one radius in length; 180° = π radians. Formulas like s = rθ only work with θ in radians — feeding in a degree measure produces a number that answers nothing.
random assignmentrandomly assigned, randomised: Assigning subjects to treatment or control at random once you already have them. This is what licenses a causal claim. Confusing it with random sampling is the single most tested idea in the statistics-claims question type.
random samplingrandom sample, randomly selected: Choosing who to study at random from a population. It licenses generalising your result to that population — and nothing more. It does not license a causal claim.
rate vs. countper capita, count for rate: A rate — a share, a proportion, a per-capita or per-100,000 figure — is a value already divided by a base; a count or total is not. The row with the highest count and the row with the highest rate are routinely different rows, and a figure prints both so both answers can be written into the choices.
rational expressionrational expressions: A fraction whose numerator and/or denominator is a polynomial, such as (x² − 9)/(x − 3). Simplifying one means factoring top and bottom and cancelling only whole shared factors.
rationalizerationalized, rationalizing: Rewriting a fraction with an irrational denominator (like 1/√2) into an equivalent form with a rational one (√2/2), by multiplying top and bottom by the same radical. The SAT prints answers already rationalized, so an unrationalized answer that isn't among the choices is usually just unsimplified, not wrong.
reference sheet: The formula sheet provided on-screen during the Math section. It covers geometry only — areas, volumes, the Pythagorean theorem, special right triangles, and circle facts. Every algebra and statistics formula you need must be in your head.
relative clauserelative clauses: A clause beginning with who, which, or that, describing the noun immediately before it. Like a prepositional phrase, it can sit between a subject and its verb without ever being the subject itself.
relative pronounrelative pronouns: Who, which, that, whose, or where, used to open a clause that points back at a noun in another clause. A clause that starts with one can never stand alone as a sentence.
restrictive clausenonrestrictive clause, restrictive, nonrestrictive: A restrictive clause narrows which noun is meant and takes no commas ("that" clauses); a nonrestrictive clause adds extra information about a noun already identified and is set off with commas ("which" clauses, in edited American English). Swapping one for the other changes what the sentence claims, not just its grammar.
retrieval practiceretrieval, testing effect, active recall: Producing an answer from memory, rather than reviewing one. It is the single best-supported study technique there is, and it is the reason every lesson here ends in questions instead of a summary.
reverse percentage: A problem that hands you the value after a percent change, or a chain of them, and asks for the value before it. Solved by dividing the after-value by the combined multiplier, never by subtracting the percent back off — which this course names as the standard wrong move.

S

sampling frameframe, the frame, sampling frames: The actual list or population a sample was physically drawn from — a magazine's subscriber list, a registered-voter roll — as opposed to the wider population a claim is about. Random selection only generalises to the frame, not beyond it, so a frame that quietly excludes part of the target population undercuts the claim no matter how random the draw was.
sampling variabilitysampling wobble: How much an estimate would differ across repeated random samples drawn the same way, purely from which members happened to be picked. It is the one thing a margin of error measures — and the only thing.
scale factorscale factors, scaled by a factor: The single number a dilation or similarity transformation multiplies every length by. Lengths scale by k, areas by k², volumes by k³ — a 1:20 model has 1/400 the surface area and 1/8,000 the volume of the real thing.
scaled scorescaled, scaling, equating: Your raw number correct is converted to the 200–800 per-section scale through a process that accounts for both the difficulty of the specific questions you saw and which module you were routed to. This is why two people with the same number correct can score differently.
secant (line)secant: A line that cuts through a circle at two points, as opposed to a tangent, which touches at one. Distinct from the secant trigonometric ratio, which shares the name but not the meaning.
sector (of a circle)sectors, circular sector: The pie-slice region of a circle bounded by two radii and the arc between them, with area (θ/360)·πr² for a central angle θ in degrees — the same fraction of the circle's area that the arc is of its circumference.
selection effectselection bias: A difference between two groups that existed before a study began, rather than one caused by whatever the study is testing. It's the strongest weakener of a causal conclusion because it explains the result without the tested cause doing anything, and it never has to contradict a single reported fact.
self-explanationself-explain, elaborative interrogation: Saying, in your own words, why a step works. The benefit comes from generating the sentence, not from its quality — which is why nothing here grades it and it is still worth doing.
similar trianglessimilarity, similar, AA similarity, angle-angle: Triangles with identical angle measures and sides in one constant ratio, the scale factor. Two equal angle pairs (AA) is always enough to prove it — a triangle's third angle is never independent information — and that shared ratio is what licenses reusing a length or trigonometric ratio across triangles of different sizes.
skewskewed, skewed right, skewed left, right-skewed, left-skewed: The direction a distribution's tail stretches — right-skewed if the tail runs toward high values, left-skewed if it runs toward low ones. Named for the tail, not for where most of the data sits, which is why it's easy to get backwards under time pressure.
slopegradient, rate of change: How much the output changes for every one-unit increase in the input — the m in y = mx + b. It always carries units: dollars per hour, centimetres per minute, y-units per x-unit.
slope-intercept formy = mx + b: The equation y = mx + b, which displays a line's slope and y-intercept directly — the form most "write an equation" items expect as a final answer.
space diagonalspace diagonals: The diagonal running through the interior of a 3D solid, connecting a vertex to the vertex farthest from it — for a rectangular box with edges l, w, h it equals √(l² + w² + h²), the Pythagorean theorem applied twice.
spacingspaced practice, spaced repetition, distributed practice: Spreading study of one topic across separate sessions rather than massing it into one. Reliably beats cramming for anything you need to still know weeks later — and the optimal gap grows as the date you need it recedes.
standard deviation: A measure of how spread out a set of values is around its mean. Larger means more spread. On the SAT you compare it between data sets rather than compute it — the arithmetic is never required.
standard error of measurementstandard error, SEM, error band: The amount a score would be expected to wobble if you retook an equivalent test without learning anything in between. It is why a single score is honestly written as a range, and why a 20-point change between two practice tests is usually noise rather than progress.
standard form (linear equation)standard form, Ax + By = C: A linear equation written as Ax + By = C, with both variable terms on one side and the constant alone on the other. Its slope is −A/B and its y-intercept is C/B — neither can be read off directly the way it can from slope-intercept form — and it's the arrangement the coefficient-comparison rule for systems needs before any coefficients can be safely compared.
stemstems, question stem: The question portion of an item, as distinct from its answer choices — "Which choice best states the main idea of the text?" is a stem, and so is "What is the value of x?" Reading it fully before the choices matters on every domain, not just Reading & Writing.
strong pathweak path: This course's name for solving an inequality by moving variable terms to whichever side keeps the coefficient positive, so the solver never has to divide by a negative and never has to remember to flip the symbol. Contrasted with the "weak path," which reaches the same answer but passes through a division-by-negative step.
subjectsubjects: The noun or pronoun a sentence's main verb belongs to — the who or the what that is doing the verb, or being described by it. Find the main verb first, then ask who or what is doing it, and that answer is the subject; it is never sitting inside a prepositional phrase, which is why "one of the students" has "one" as its subject, not "students."
subject-verb agreementsubject-verb, verb agreement: The requirement that a verb match its subject in number — a singular subject takes a singular verb form, a plural subject takes a plural one: "the kettle boils," never "the kettle boil"; "the kettles boil," never "the kettles boils." The test almost never breaks this rule where the subject and verb sit side by side; it hides a plural noun inside a prepositional phrase or a supplement between them, so a careless reader matches the verb to the nearest noun instead of the actual subject.
subordinating conjunctionsubordinator, subordinators: A word like "because," "although," "while," or "since" placed at the front of a clause that makes it dependent — unable to stand alone as a sentence — no matter how complete the clause looks otherwise.
substitutionsubstitution method, substitute: Solving a system by isolating one variable in one equation, then replacing that variable with its equivalent expression everywhere it appears in the other equation.
successive percent changechained percent change, compound percent change: Two or more percent changes applied one after another — a markup then a discount, a discount then a tax, a rate compounding over several years. Combined by multiplying each change's multiplier together, never by adding the percents; the gap between the two methods is the cross-term in (1 + a)(1 + b), and it grows with the size of the percents.
supplementsupplements, nonessential clause: Material that can be lifted out of a sentence without breaking it or changing its core meaning, bracketed by a matching pair of marks — comma with comma, dash with dash, parentheses with parentheses. Tested by deleting the material and checking that what remains still reads as a full sentence.
supplementary anglessupplementary: Two angles whose measures sum to 180° — a linear pair, or a same-side-interior pair across parallel lines. Confused with complementary far more often than the vocabulary difficulty would suggest.

T

tangent (to a circle)tangent line, point of tangency: A line that touches a circle at exactly one point, always perpendicular to the radius drawn to that point. Not to be confused with the tangent ratio in trigonometry — same word, unrelated meaning.
test pointtest points, point-testing: The technique for deciding which side of a boundary line to shade: substitute any point not on the line into the original inequality and see whether the statement holds. One substitution settles the entire, infinite region, and it works even when isolating a variable with a negative coefficient has distorted the inequality's symbol.
the turnsetup and turn: The point in a non-fiction passage where it pivots from a setup — background, a standard account, a definition — to its own actual claim, signaled by words like "but," "however," or "in fact." The main idea lives on the far side of the turn, not in the setup.
transversaltransversals: A line that cuts across two other lines — most often two parallel lines — creating a set of angles at each crossing that every later angle-chasing question is built from.
true but irrelevanttrue-but-irrelevant: The single most common wrong-answer pattern on quantitative evidence questions: a statement that is accurate to the figure but supports a different claim than the one the sentence actually makes.
true-but-subordinate: A wrong-answer family on Reading main-idea items: a choice that restates something the passage genuinely says, but that is a supporting detail rather than the claim the passage exists to make. The single most common distractor type on Central Ideas & Details items.
two-view texttwo-view passage, dual-viewpoint text: A passage that presents two scholars', researchers', or characters' competing claims about the same question. Evaluating a choice against the wrong one of the two is one of the most common ways a strong reader loses a point on this passage type.
two-way frequency tabletwo-way table, frequency table: A table classifying one group by two traits at once — rows are one trait's categories, columns the other's, each interior cell holds a count, and the margins hold row and column totals. Almost every probability item on the digital SAT is built on one.

U

undercoverageundercoverage bias: When a sampling frame systematically excludes part of the population a claim is about, so those excluded people had zero chance of selection — distinct from nonresponse, where they had a chance but didn't take it.
unit circle: A circle of radius 1 centred at the origin, used to define sine and cosine for any angle as the y- and x-coordinates of the point that angle sweeps to. Distinct from an ordinary circle item — coordinates on it are ratios, not lengths.
unit rateunit rates: A rate rewritten with 1 in the denominator — 60 miles per 1 hour rather than 240 miles per 4 hours. Reducing to the unit rate first is what turns most rate, ratio, and proportion problems into a single line of arithmetic.

V

verbverbs, main verb: A word that names what a subject does or is — boiled, discovered, seems, remained. A sentence needs one that belongs to its own subject to count as complete, because asserting that something happened, is happening, or is true is a job no other kind of word can do. When a sentence buries its real verb behind an attached clause or phrase, the one that actually belongs to the subject is the main verb.
vertex (of a parabola)vertices: The point where a parabola turns — its minimum if the parabola opens upward, its maximum if it opens downward. In vertex form a(x−h)² + k, the vertex is (h, k).
vertical anglesvertical angle: The pair of angles directly opposite each other where two lines cross. Always equal, regardless of any other fact about the figure.
voluntary responsevoluntary-response sample, self-selected sample: A sample where participants choose for themselves whether to be included, rather than being drawn by the researcher. Systematically overrepresents whoever cares enough about the topic to respond, and collecting more responses does not fix it — bias does not shrink with sample size.

W

worked exampleworked examples, fading, faded: A fully solved problem studied before attempting one yourself. They work best when they fade: each one hides more of the ending than the last, until you're solving unaided. Jumping straight to unassisted problems wastes effort; never fading leaves you able to follow a solution but not produce one.

Y

y-interceptintercept, y intercept: The value of y when x is zero — where the line crosses the vertical axis, and in a real-world model, the starting amount, the fixed fee, the value before anything has happened yet.

Z

zero of a functionroot (of a function), x-intercept: An input that makes a function's output zero — visible on a graph as the x-intercept. Distinct from the y-intercept: f(0) is the y-intercept, while a zero of f is the input where f(x) = 0.
zero-product property: If two real numbers multiply to zero, at least one of them must be zero. It is the only fact that licenses splitting a factored equation into two solvable ones, and it only applies when the product actually equals zero — not any other number.