ACT English Terms: Complete Grammar & Rhetoric Reference
Every concept tested on the ACT English section — 7 comma rules, all punctuation marks with examples, 15 tricky subject-verb agreement cases, rhetorical skills, 200+ transition words by function, style and clarity, and 50+ commonly confused word pairs.
Punctuation · Grammar · Rhetoric · Transitions · Confused words
Complete Punctuation Guide
Punctuation accounts for roughly 35% of ACT English questions. Every rule below has been tested on recent ACT exams.
Comma — 7 Rules
Wrong: “The experiment ran for three weeks and the results were conclusive.”
Correct: “The experiment ran for three weeks, and the results were conclusive.”
Without the comma, the two independent clauses create a run-on.
Correct: “The sample was small, but the effect size was large enough to be meaningful.”
Correct: “Funding was cut, so the team pivoted to a less expensive methodology.”
Wrong: “When the temperature dropped below zero the reaction slowed significantly.”
Correct: “When the temperature dropped below zero, the reaction slowed significantly.”
Correct: “After reviewing all available evidence, the committee issued its recommendation.”
Correct: “Having completed the analysis, the researchers submitted their manuscript.”
Correct: “To minimize error, the team ran each trial three times.”
Correct: “In the context of evolutionary biology, this finding has significant implications.”
Wrong: “Dr. Harrison the lead researcher presented the findings.”
Correct: “Dr. Harrison, the lead researcher, presented the findings.”
Correct: “The new drug, which was approved last year, has already reached 2 million patients.”
'Which' introduces a nonrestrictive clause — use commas. 'That' introduces a restrictive clause — no commas.
Correct: “The proposal, though expensive, received unanimous approval.”
Correct: “Carbon dioxide, a greenhouse gas, traps heat in the atmosphere.”
Wrong: “The study examined income, education and health outcomes.”
Correct: “The study examined income, education, and health outcomes.”
ACT prefers the Oxford comma.
Correct: “Researchers collected samples, conducted analyses, and published their conclusions.”
Correct: “A thorough, well-documented study requires time and resources.”
'Thorough and well-documented' works — comma needed.
Correct: “A large red dataset appeared on the screen.”
'Large and red dataset' is awkward — no comma. These are not coordinate.
Correct: “The author concludes, "The evidence compels action."”
Correct: “The scientist stated, "No conclusion can be drawn from a single data point."”
Wrong: “The committee, reached a decision after deliberating for three hours.”
Correct: “The committee reached a decision after deliberating for three hours.”
Wrong: “The study confirmed, that exercise reduces the risk of chronic disease.”
Correct: “The study confirmed that exercise reduces the risk of chronic disease.”
Semicolon — 3 Rules
Wrong: “Although the first trial failed; the second produced clear results.”
Correct: “The first trial failed; the second produced clear results.”
Wrong because 'Although the first trial failed' is a dependent clause — cannot use a semicolon.
Wrong: “The sample was small, however, the effect size was large.”
Correct: “The sample was small; however, the effect size was large.”
'However' is not a coordinating conjunction — a comma before it creates a comma splice.
Correct: “The results were unexpected; therefore, the team delayed publication.”
Correct: “Funding was insufficient; consequently, two planned trials were cancelled.”
Wrong: “The study sites were Chicago, Illinois, Austin, Texas, and Portland, Oregon.”
Correct: “The study sites were Chicago, Illinois; Austin, Texas; and Portland, Oregon.”
Colon
Wrong: “The variables measured were: temperature, humidity, and pressure.”
Correct: “Three variables were measured: temperature, humidity, and pressure.”
Wrong because 'The variables measured were' is not a complete clause.
Correct: “The author makes one central claim: that economic inequality drives political instability.”
Correct: “The conclusion was startling: not one of the three trials produced a positive result.”
Dash (Em Dash)
Correct: “Only one obstacle remained — funding.”
Wrong: “The finding — unexpected by the entire research team, overturned decades of consensus.”
Correct: “The finding — unexpected by the entire research team — overturned decades of consensus.”
When you open a dash, you must close with another dash, not a comma.
Apostrophe
Possessive plural ending in s: Add only ' (the scientists' findings).
Contractions: it's = it is; they're = they are; you're = you are; who's = who is.
Never use apostrophes for plurals: Wrong: “the 1990's.” Correct: “the 1990s.”
Correct: “The team's results were published in a peer-reviewed journal.”
Correct: “It's [it is] clear that the model has its [possessive] limitations.”
Correct: “The three researchers' contributions were each acknowledged.”
Parentheses
Correct: “The compound (see Figure 2) exhibits unusual thermal properties.”
Correct: “Two of the participants (both under age 25) reported no side effects.”
Usage & Mechanics
Subject-Verb Agreement — 15 Tricky Cases
The subject is not in the prepositional phrase. Find the true subject.
Wrong: “The list of participants were extensive.”
Correct: “The list of participants was extensive. [Subject: 'list']”
When the subject follows the verb, find it before choosing the verb.
Wrong: “Here is the results.”
Correct: “Here are the results. [Subject: 'results']”
Two subjects joined by 'and' are usually plural.
Correct: “The director and the board have approved the proposal.”
The verb agrees with the nearer subject.
Correct: “Neither the participants nor the researcher was aware of the hypothesis. ['researcher' is closer — singular]”
Treat as singular in formal ACT usage (committee, team, jury, staff, audience).
Wrong: “The committee have reached a verdict.”
Correct: “The committee has reached a verdict.”
Everyone, anyone, someone, no one, nobody, each, either, neither take singular verbs.
Wrong: “Everyone in the trial groups were given the same dose.”
Correct: “Everyone in the trial groups was given the same dose.”
'The number' = singular. 'A number of' = plural.
Correct: “The number of applicants is rising. A number of applicants are qualified.”
In formal/scientific contexts, 'data' is plural.
Wrong: “The data suggests a correlation.”
Correct: “The data suggest a correlation.”
These words look plural but are singular in meaning.
Correct: “The news is encouraging. Mathematics is required for the degree.”
The verb in the relative clause agrees with the antecedent of who/that/which.
Wrong: “She is one of the researchers who has replicated the results.”
Correct: “She is one of the researchers who have replicated the results. [Antecedent: 'researchers']”
Agreement depends on the noun that follows 'of.'
Correct: “Three-quarters of the data is missing. Three-quarters of the samples are missing.”
These are treated as singular units.
Correct: “Five years is a long time to wait. Twenty dollars is the entry fee.”
Even plural-sounding titles take a singular verb.
Correct: “The Grapes of Wrath is considered Steinbeck's masterpiece.”
These phrases do not make the subject plural — the original subject still controls the verb.
Wrong: “The doctor, as well as the nurses, were present at the meeting.”
Correct: “The doctor, as well as the nurses, was present at the meeting.”
'Each' is singular; 'all' and 'both' are plural.
Correct: “Each of the trials was conducted twice. All of the trials were conducted twice.”
Pronoun Case
Wrong: “Between you and I, the methodology was flawed.”
Correct: “Between you and me, the methodology was flawed.”
'Between' is a preposition — use objective 'me.'
Wrong: “The award was given to she and her co-author.”
Correct: “The award was given to her and her co-author.”
Correct: “The researcher who discovered the compound won the prize.”
'Who' is subject of 'discovered.'
Correct: “The researcher whom the committee awarded received the prize.”
'Whom' is object of 'awarded.'
Modifier Placement
Wrong: “Having analyzed the data, a conclusion was reached.”
Correct: “Having analyzed the data, the team reached a conclusion.”
The conclusion did not analyze the data — the team did.
Wrong: “Exhausted after the experiment, the weekend was taken off.”
Correct: “Exhausted after the experiment, the researcher took the weekend off.”
Parallel Structure
Wrong: “The researcher analyzed data, wrote the report, and was presenting her conclusions.”
Correct: “The researcher analyzed data, wrote the report, and presented her conclusions.”
Wrong: “Both the cost improved and quality significantly improved.”
Correct: “Both the cost and the quality improved significantly.”
Wrong: “Not only did the drug reduce pain, but recovery time was also shortened.”
Correct: “Not only did the drug reduce pain, but it also shortened recovery time.”
Verb Tense
Wrong: “Darwin observed the variation and proposes his theory of natural selection.”
Correct: “Darwin observed the variation and proposed his theory of natural selection.”
Correct: “If the experiment were replicated today, the results might differ.”
Subjunctive mood for hypothetical conditions.
Rhetorical Skills
The ACT's Rhetorical Skills questions (about 35% of English) test your ability to improve the effectiveness, organization, and style of writing — not just correctness.
Strategy Questions
A: Read the question carefully. It will describe a specific goal (e.g., 'provide a concrete example,' 'introduce a counterargument,' 'establish the author's qualifications'). Evaluate each answer choice against that precise goal — not your general opinion of the writing.
A: Ask: does the sentence support the paragraph's main idea? Does it provide evidence, elaboration, or a smooth transition? If it introduces a tangential topic or repeats something already stated, choose 'No.'
A: Identify the purpose of the sentence. If it supports the paragraph's focus, keep it. If it introduces an irrelevant topic or contradicts the passage's main argument, delete it.
A: Identify the paragraph's main idea first. The most relevant sentence directly supports that idea — it does not merely mention related topics or expand into new territory.
Organization Questions
Relevance (OMIT Questions)
Decision process for OMIT questions:
- Identify the paragraph's primary purpose in one sentence.
- Ask: does this sentence directly support that purpose?
- If yes, keep it. If it wanders into unrelated territory, delete it.
- The fact that a sentence is interesting or factually true is not sufficient reason to keep it — it must be relevant.
200+ Transition Words by Function
The ACT English section tests transitions more than any other single rhetorical skill. The key is matching the logical relationship — not just finding a word that “sounds right.”
Contrast / Opposition
Use when the second idea contradicts, limits, or qualifies the first. 'However' needs a semicolon before it; 'but' needs only a comma.
Cause and Effect / Result
Use when the second idea results from the first. 'Thus' is more formal; 'so' is informal but acceptable.
Addition / Support
Use when adding a new, related supporting point. 'Indeed' and 'in fact' intensify the same point; 'furthermore' and 'moreover' add a new point.
Example / Illustration
Use when introducing a specific example to support a general claim.
Emphasis / Intensification
Use when stressing the importance of what follows.
Clarification / Restatement
Use when restating or explaining more clearly what was just said.
Sequence / Time Order
Use to organize steps, stages, or events chronologically.
Concession
Use when acknowledging the merit of an opposing point before countering it.
Summary / Conclusion
Use at the end of an argument. Avoid using 'therefore' as a summary word — it signals a logical consequence, not a conclusion.
Style: Wordiness, Redundancy, and Clarity
The ACT rewards concise, precise writing. A significant category of questions asks you to eliminate unnecessary words without changing the meaning.
Redundancy — Before and After Examples
Wordiness — Replacing Wordy Phrases
Clarity — Avoid Vague Pronouns
Wrong: “The researchers questioned the model's assumptions. This failed to account for regional variation.”
Correct: “The researchers questioned the model's assumptions, arguing that the model failed to account for regional variation.”
What does 'this' refer to? The questioning? The model? The assumptions?
50+ Commonly Confused Words Tested on ACT
The ACT English section regularly tests words that are confused for each other. Mastering these pairs is high-yield preparation.
| Word 1 | Definition | Word 2 | Definition | Example |
|---|---|---|---|---|
| affect | verb: to influence or have an impact on | effect | noun: the result or outcome; verb (rare): to bring about | The weather affected (v) our plans. The effect (n) was a two-day delay. The new policy effected (v) real change. |
| lay | verb: to place or put something down (requires an object) | lie | verb: to recline or rest (no object needed) | Lay the book on the table. I need to lie down. (Past: laid the book; lay down yesterday) |
| its | possessive pronoun: belonging to it | it's | contraction: it is / it has | The study has its (possessive) limitations. It's (it is) unclear whether the results will replicate. |
| who | subjective case pronoun: used as the subject of a clause | whom | objective case pronoun: used as the object of a verb or preposition | The scientist who (subject) led the team. The scientist whom (object) the committee chose. |
| which | relative pronoun for nonessential clauses (use with commas) | that | relative pronoun for essential (restrictive) clauses (no commas) | The study, which used 500 participants, was published last year. The study that used 500 participants showed the strongest results. |
| less | for uncountable/mass nouns (less water, less time, less effort) | fewer | for countable nouns (fewer students, fewer errors, fewer days) | There is less rainfall this year. There are fewer rainy days this year. |
| among | use for three or more items or people | between | use for exactly two items or people | The prize was divided among the five winners. The prize was divided between the two finalists. |
| further | figurative distance: to a greater degree, more (further discussion) | farther | physical distance: greater actual distance (farther down the road) | We need to discuss this further. The second town is farther from the highway. |
| imply | to suggest or hint at something without stating it directly (speaker implies) | infer | to deduce or conclude something from evidence (listener infers) | The author implied that the policy had failed. Readers inferred from the data that the policy had failed. |
| complement | to complete or go well with; something that completes | compliment | to express praise; an expression of praise | The red sauce complements the pasta perfectly. She complimented the chef on the sauce. |
| principal | adjective: main, primary; noun: the head of a school; a capital sum | principle | noun: a fundamental truth, rule, or belief | The principal reason for the delay was funding. The scientist refused to compromise her principles. |
| accept | to receive willingly; to agree to | except | preposition: not including; verb: to exclude | She accepted the award graciously. Every lab except one reported the same result. |
| elicit | to draw out or evoke a response (a verb) | illicit | adjective: forbidden by law or custom; illegal | The survey was designed to elicit honest opinions. The investigation uncovered illicit financial transactions. |
| eminent | famous and respected, especially in a profession | imminent | about to happen very soon | An eminent scientist chaired the review panel. A third outbreak appeared imminent. |
| tortuous | full of twists and turns; complex and lengthy | torturous | causing severe physical or mental suffering; like torture | The tortuous path up the mountain took three hours. The waiting was torturous for the anxious students. |
| discreet | careful and circumspect in speech; keeping confidences | discrete | individually distinct and separate; not continuous | She was discreet about her colleagues' personal struggles. The data were divided into three discrete categories. |
| adverse | harmful or unfavorable (adverse conditions, adverse effects) | averse | having a strong dislike of or opposition to something | The drug had several adverse side effects. The committee was averse to any dramatic policy changes. |
| assure | to tell someone something positively or confidently | ensure | to make certain that something happens | I can assure you the results are accurate. Double-checking ensures the results are accurate. |
| stationary | adjective: not moving or not changing | stationery | noun: writing materials, especially paper and envelopes | The satellite remained stationary in orbit. The office ran out of stationery. |
| historic | famous or important in history | historical | relating to history; of or concerning the past | The moon landing was a historic event. The passage provides a historical account of the period. |
| economic | relating to economics or the economy | economical | providing good value relative to cost; thrifty | The economic impact of the policy was significant. An economical car uses less fuel per mile. |
| comprise | to consist of; the whole comprises the parts | compose | to make up; the parts compose the whole | The committee comprises twelve members. Twelve members compose the committee. |
| nauseated | feeling nausea; feeling sick | nauseous | causing nausea in others (formal usage) | I felt nauseated after reading the report. The chemical smell was nauseous. |
| continual | repeatedly occurring (can stop and restart) | continuous | occurring without interruption; unbroken | He faced continual interruptions throughout the day. The machine runs on a continuous loop. |
| credible | able to be believed; convincing | credulous | too willing to believe things; gullible | The witness gave a credible account of events. Only the most credulous readers would accept that claim at face value. |
| sensory | relating to the physical senses | sensuous | relating to or affecting the senses aesthetically; pleasing to the senses | The experiment measured sensory thresholds. The poem's sensuous imagery appeals to smell and touch. |
| alternate | adjective: every other one; verb: to switch back and forth | alternative | noun/adjective: one of two or more available options | We met on alternate Fridays. Solar energy is a viable alternative to fossil fuels. |
| amiable | having a friendly and pleasant manner | amicable | done in a friendly spirit; without hostility (used for agreements/settlements) | The amiable professor was happy to discuss ideas after class. The two parties reached an amicable settlement. |
| mitigate | to make something less severe or serious | militate | to be a strong influence against something | Early intervention mitigates the long-term effects. The high cost militates against widespread adoption. |
| flaunt | to display something ostentatiously | flout | to openly disregard a rule or convention | He flaunted his success with an expensive car. The company routinely flouted environmental regulations. |
| liable | legally responsible; likely to do something undesirable | libel | a published false statement that harms someone's reputation | The company is liable for the accident. The article was found to constitute libel. |
| precede | to come before in time or order | proceed | to begin or continue a course of action | A brief orientation preceded the main session. After the break, the workshop will proceed. |
| persecute | to subject to hostility or ill-treatment because of religion, race, beliefs, etc. | prosecute | to take legal action against someone in a court of law | The minority group was systematically persecuted. The company was prosecuted for fraud. |
| regrettable | causing regret; unfortunate (describes an event or situation) | regretful | feeling or expressing regret (describes a person's emotion) | The delay was regrettable. She was regretful about missing the ceremony. |
| notable | worthy of attention; remarkable | notorious | famous for something bad; widely known unfavorably | The report made several notable findings. The company became notorious for cutting corners on safety. |
| prodigal | spending money or resources recklessly; wastefully extravagant | prodigious | remarkably great in extent, size, or degree | The prodigal heir squandered the estate in three years. She had a prodigious talent for mathematics. |
| venal | susceptible to bribery; corrupt | venial | of a fault or offense: slight and pardonable | The venal official accepted payments to ignore violations. The student was forgiven for the venial error. |
| loathe | to feel intense dislike or disgust for | loath | reluctant; unwilling | She loathed the practice of citing anecdote as evidence. He was loath to abandon a theory he had spent years developing. |
| endemic | regularly found among particular people or in a certain area | epidemic | a widespread occurrence of an infectious disease in a community at a particular time | Corruption was endemic to the institution. An epidemic of influenza swept through the city. |
| uninterested | not interested; indifferent | disinterested | impartial; free from bias or self-interest | He was completely uninterested in the topic. A disinterested arbitrator was needed to resolve the dispute. |
| council | a formal body of people convened for consultation or governance | counsel | noun: advice; verb: to give advice | The city council voted to approve the proposal. The committee counseled caution. |
| capitol | the building housing a legislature | capital | a city serving as a seat of government; money or assets; punishable by death | The state capitol is undergoing renovation. Austin is the capital of Texas. The startup needed more capital. |
| appraise | to assess the value or quality of something | apprise | to inform or notify someone of something | An independent assessor appraised the property. The team was apprised of the new findings immediately. |
| precipitate | adjective: rash, hasty; verb: to cause something to happen suddenly | precipitation | noun: moisture falling as rain or snow; or the rash quality | His precipitate departure surprised everyone. Heavy precipitation disrupted the outdoor trial. |
| permeate | to spread throughout something | perimeter | the boundary or outer edge of a shape or area | The aroma of the compound permeated the entire laboratory. The perimeter of the field was marked with sensors. |
| sensible | done or chosen in accordance with wisdom; practical and reasonable | sensitive | quick to detect or respond; easily upset or damaged | A sensible investment strategy avoids excessive risk. The instrument is sensitive to changes of less than 0.001 degrees. |
| moral | adjective: concerned with principles of right and wrong; noun: a lesson | morale | noun: the confidence, enthusiasm, and discipline of a person or group | The scientist faced a moral dilemma. After three failed trials, team morale was low. |
| forbid | to refuse to allow something; to prohibit | prohibit | to formally forbid by law or rule | The committee forbade the use of unapproved methods. The regulation prohibits the discharge of certain chemicals. |
| incredible | impossible to believe; extraordinary (informal: very good) | incredulous | unwilling or unable to believe something; skeptical | The speed of the recovery was incredible. She was incredulous when told that the results had been fabricated. |
| luxurious | extremely comfortable and expensive | luxuriant | rich and profuse in growth; lush and abundant | The research vessel was outfitted with surprisingly luxurious quarters. The forest was luxuriant with ferns and mosses. |
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