ACT Science vocabulary: models, claims and evidence.
20 terms the ACT Science section expects you to already know when a passage turns to models, claims and evidence — each with a definition, an example sentence, and a memory cue.
ACT Science does not test whether you can define these words — it tests whether you can read a figure fast enough, and an unfamiliar term is what stops you. The section gives you well under a minute per question, so the goal here is recognition, not recall: you want to meet these terms in a question stem and know immediately what they point to.
Read the definition, then the example, then the memory cue. Come back a few days later and cover the definitions — recalling a term cold is what fixes it, and rereading it is not.
The 20 terms
Alphabetical. Everything in the Models, Claims & Evidence guide.
01
conclusionnoun
The claim that an argument's supporting reasons are intended to establish.
Although the survey shows a correlation, the committee's conclusion claims a causal relationship without further evidence.
Memory cueAt the close of a reasoning chain sits its destination claim: the conclusion.
02
conjecturenoun/verb
An opinion formed on the basis of incomplete information; to form such an opinion
Without hard evidence, any explanation at this point is merely conjecture .
Memory cueConjecture sketches a conclusion in pencil because the evidence is incomplete.
03
corroboratedverb (past tense)
Confirmed or gave support to (a statement, theory, or finding)
Eyewitness testimony corroborated the forensic evidence, strengthening the prosecution's case considerably.
Memory cueA second witness corroborated the story by adding independent support.
04
counterexamplenoun
An example that disproves or contradicts a general claim
A single counterexample is sufficient to disprove a universal claim in formal logic.
Memory cueOne black swan is a counterexample disproving “all swans are white.”
05
definitiveadjective
Done or reached decisively and with authority; providing a final, authoritative answer
Her biography of the composer is widely regarded as the definitive account of his life and work.
Memory cueA definitive answer stamps the question FINAL with decisive authority.
06
fallaciousadjective
Based on a mistaken belief; embodying a fallacy; logically unsound
The argument that correlation implies causation is a classic example of fallacious reasoning.
Memory cueA fallacious argument contains a logical fall and cannot support its conclusion.
07
falsifiableadjective
Capable of being tested in a way that could show a claim to be false.
The hypothesis is falsifiable because a measured decrease in growth would directly contradict its prediction.
Memory cueA falsifiable claim leaves an unlocked door through which contrary evidence could defeat it.
08
inconclusiveadjective
Not leading to a firm conclusion; not decisive
The autopsy results were inconclusive , leaving investigators without a definitive cause of death.
Memory cueInconclusive evidence ends with a question mark instead of a final verdict.
09
inferencenoun
A conclusion reached by reasoning from stated facts rather than by direct statement.
From the repeated references to drought, readers can draw the inference that water shaped the migration.
Memory cueClues enter a funnel and a reasonable new idea emerges; that idea is an inference.
10
limitationnoun
A feature of a method, dataset, or model that restricts what can reasonably be concluded.
The short observation period is a limitation because delayed effects would remain entirely undetected.
Memory cueA limitation is a boundary fence around what the study can safely claim.
11
modelnoun
A simplified representation used to explain, describe, or predict how a system behaves.
The climate model predicts regional rainfall by representing interactions among oceans, land, and the atmosphere.
Memory cueA model is a manageable stand-in that helps explain a larger, more complicated system.
12
plausibleadjective
seeming reasonable or probable; believable.
Her explanation seemed plausible because the timeline matched every piece of available evidence, showing how the term functions naturally in an everyday academic context.
Memory cueA plausible explanation crosses the bridge marked REASONABLE AND BELIEVABLE.
13
premisenoun
A proposition from which another is inferred or follows as a conclusion; the basis of an argument
The entire argument rests on a premise that the author never actually defends—that human nature is fundamentally selfish.
Memory cueA premise is the starting platform from which an argument’s conclusion rises.
14
presumptionnoun
A belief accepted as true without proof; an assumption
The legal system operates on the presumption that a defendant is innocent until proven guilty beyond a reasonable doubt.
Memory cueA presumption takes a belief as true before proof arrives.
15
refuteverb
To prove a statement or theory to be wrong or false
The archaeologist presented compelling evidence to refute the long-standing claim that the site was a ceremonial center.
Memory cueRefute a false claim by striking it with decisive contrary evidence.
16
replicationnoun
The repetition of a study or experiment to determine whether its result can be reproduced.
Successful replication by an independent laboratory increased confidence that the unusual effect was genuine.
Memory cueReplication presses the experiment's copy button to see whether the same result appears again.
17
speculativeadjective
Based on conjecture or theory rather than firm evidence; tentative
The final chapter ventures into speculative territory, imagining how the technology might evolve over the next century.
Memory cueA speculative claim is penciled in because evidence remains uncertain.
18
substantiateverb
to provide evidence to support or prove the truth of something.
Can you substantiate your claims with documentation, giving observers evidence for deciding whether the claim could be trusted.
Memory cueSubstantiate a statement by stacking evidence beneath its claim.
19
validitynoun
The degree to which evidence or a method supports the conclusion it is intended to support.
The experiment's validity weakened because the two groups differed in both temperature and light exposure.
Memory cueValidity asks whether the evidence bridge truly reaches the conclusion it claims to support.
20
verifiableadjective
Capable of being tested or confirmed through reliable evidence.
The panel requested verifiable records instead of relying on the consultant's unsupported recollection of events.
Memory cueIf a claim can earn a verified checkmark after inspection, it is verifiable.
Knowing the words is step one — reading the figure is step two.
Test Ninjas puts these terms back into real Science passages — full-length ACT practice tests, a complete Science course, and an explanation on every question.
