The 75 questions on the ACT English section divide into two broad areas: Production of Writing (organization, development, and cohesion) and Knowledge of Language (grammar, usage, and punctuation). The 50 rules below cover everything tested under Knowledge of Language — the category where most students leave points on the table. These rules are organized into three groups: Sentence Structure & Formation, Usage Conventions, and Punctuation.

Part 1: Sentence Structure & Formation (Rules 1–16)

Sentence structure questions ask you to identify whether a sentence is grammatically complete, whether clauses are joined correctly, and whether modifying phrases and parallel elements are constructed properly. These 16 rules cover the most commonly tested structural errors on the ACT.

1 Joining independent clauses with punctuation or conjunctions

Two independent clauses must be joined by a comma plus a coordinating conjunction (for, and, nor, but, or, yet, so — the FANBOYS), a semicolon, or a period. A comma alone between two independent clauses is a comma splice.

ACT Tip: Two complete sentences with only a comma between them — that’s a comma splice, always wrong. Add a FANBOYS conjunction after the comma, or replace the comma with a semicolon.

2 Avoiding fused (run-on) sentences

A fused sentence joins two independent clauses with no punctuation or conjunction at all. Fix it with a period, a semicolon, or a comma plus a FANBOYS conjunction.

ACT Tip: Find the main verb of each clause. Two complete thoughts with nothing between them — that’s a run-on. Look for where one idea ends and a new subject-verb pair begins.

3 Avoiding sentence fragments

Every sentence needs a subject, a predicate, and a complete thought. A dependent clause or participial phrase standing alone is a fragment.

ACT Tip: Subordinating conjunctions — although, because, since, while, if, when — create dependent clauses that can never stand alone. They need a main clause attached.

4 Faulty subordination and coordination

The conjunction you pick signals the logical relationship between clauses. Using “although” when you mean “because,” or “and” when you mean “but,” is faulty coordination or subordination.

ACT Tip: What’s the relationship — contrast, cause-effect, addition? Match the conjunction to the meaning. “Although” signals contrast and can’t introduce a result.

5 Verb tense shifts within a sentence

Verb tense should stay consistent within a sentence unless a change in time is logically required. Jumping from past to present inside the same clause without a reason is an error.

ACT Tip: If both actions happen at the same time, both verbs belong in the same tense. Don’t shift unless the timeline actually changes.

6 Verb tense consistency across sentences

Tense should stay consistent throughout a paragraph unless there’s a clear reason to shift. Check the surrounding sentences to determine which tense the passage is using.

ACT Tip: Read at least one sentence before and after the underlined portion. Tense is determined by context — never evaluate it in isolation.

7 Verb voice consistency

Unnecessary shifts between active voice (the subject performs the action) and passive voice (the subject receives the action) within the same sentence create consistency errors.

ACT Tip: Active voice is almost always preferred on the ACT when both options are grammatically correct. Passive constructions are wordier and often create dangling modifier traps.

8 Pronoun person consistency

Stay in the same person throughout a sentence or passage. Shifting from “one” to “you,” or from “they” to “we,” mid-sentence is a grammatical error.

ACT Tip: The ACT regularly drops “you” or “your” into an otherwise third-person passage. That shift is almost always the wrong answer.

9 Dangling modifiers

An introductory participial or descriptive phrase must logically describe the grammatical subject of the main clause — the first noun after the comma. When it doesn’t, it dangles.

ACT Tip: Who is doing the action in the opening phrase? That person must be the grammatical subject of the sentence. If they can’t logically perform that action, the modifier dangles.

10 Misplaced modifiers

A modifier belongs as close as possible to the word it describes. The problem comes up most often with limiting words like “only,” “nearly,” “almost,” and “even.”

ACT Tip: Watch “only,” “nearly,” “almost,” and “even” — their placement changes the meaning. The best answer puts the modifier right next to the word it describes.

11 Misplaced adjectives and phrases

Adjectives and adjectival phrases belong directly before or after the noun they describe. Too far away and it becomes unclear which noun they modify.

ACT Tip: When answer choices reorder a sentence, ask which version makes it obvious which noun the modifier describes. Ambiguity is the error.

12 Missing or incorrect relative pronouns

Relative pronouns (who, whom, which, that) introduce clauses that modify nouns. Use who/whom for people and which/that for things. “That” signals an essential clause (no commas); “which” signals a non-essential clause (commas required).

ACT Tip: Using “which” for a person is always wrong. And “which” needs commas; “that” does not. If you see “which” with no commas, that’s a likely error.

13 Parallelism in a series of verbs

Verbs in a series must share the same grammatical form. Mixing infinitives, gerunds, and conjugated verbs in the same list breaks parallelism.

ACT Tip: Check the form of the first verb in the list. Every verb after it must match. First verb is an infinitive? All must be infinitives.

14 Parallelism in a series of phrases

All items in a series must follow the same grammatical pattern — noun phrase matched with noun phrase, prepositional phrase with prepositional phrase.

ACT Tip: Once you identify the pattern of the first item, every other item has to match it. First item is a gerund phrase? All items must be gerund phrases.

15 Parallelism with correlative conjunctions

Paired conjunctions — both/and, either/or, neither/nor, not only/but also — require parallel grammatical structures on both sides of the pair.

ACT Tip: Whatever form follows the first conjunction must be mirrored after the second. “Not only [adjective]” demands “but also [adjective].”

16 Imprecise conjunctions between independent clauses

Some conjunctions are grammatically acceptable but logically imprecise. The ACT rewards the conjunction that most accurately captures the relationship — cause-effect, contrast, or addition.

ACT Tip: “And” is acceptable in many places where “so,” “but,” or “because” would be more precise. Ask what the actual relationship between the clauses is, then pick the conjunction that says it best.

Part 2: Usage Conventions (Rules 17–36)

Usage questions test your command of standard English grammar conventions — verb forms, agreement, pronouns, and word choice. These rules cover the 20 most commonly tested usage errors on the ACT English section.

17 Irregular verb past tense and past participle

Irregular verbs don’t follow the standard -ed pattern. Each one has to be memorized: go/went/gone, see/saw/seen, lie/lay/lain, lay/laid/laid, bring/brought/brought.

ACT Tip: The lie/lay pair trips up most students. “Lie” (to recline) is intransitive: lie, lay, lain. “Lay” (to place something) is transitive: lay, laid, laid. “Yesterday I lay down” is correct — not “I laid down.”

18 Comparative and superlative adjective forms

Use the comparative (-er or “more”) for two things. Use the superlative (-est or “most”) for three or more. Never combine both forms — “more taller” is always wrong.

ACT Tip: Count the things being compared. Two = comparative. Three or more = superlative. Look for context clues: “of the three” or “among all” signal that a superlative is required.

19 Adjective vs. adverb

Adjectives modify nouns and pronouns. Adverbs modify verbs, adjectives, and other adverbs. After linking verbs (be, seem, look, feel, become, appear), use an adjective — not an adverb.

ACT Tip: “She ran quick” is wrong — “ran” is a verb, so the adverb “quickly” is needed. But “She felt bad” is correct — “felt” is a linking verb, so the adjective “bad” is right.

20 Correct comparative or superlative in context

Context tells you whether comparative or superlative is needed. Phrases like “of the three,” “among all the students,” or “of any” signal a superlative is required.

ACT Tip: Count before you choose. Four siblings means a superlative is required. “Younger” compares exactly two people — it can’t be right here.

21 Subject-verb agreement: basic

A verb must agree in number with its subject. Singular subjects take singular verbs; plural subjects take plural verbs. The subject is never found inside a prepositional phrase.

ACT Tip: Cross out every prepositional phrase between the subject and verb. “The list of requirements” — delete “of requirements” and you have “The list is.” Simple.

22 Subject-verb agreement: intervening phrases

A long phrase or clause between the subject and its verb doesn’t change what the verb agrees with. The verb agrees with the true subject — not whichever noun is closest.

ACT Tip: Delete everything between the subject and verb and check agreement directly. Don’t let a singular noun in the middle fool you into a singular verb for a plural subject.

23 Subject-verb agreement: inverted sentences and indefinite pronouns

In sentences beginning with “there” or “here,” the subject follows the verb. Indefinite pronouns — each, every, either, neither, anyone, everyone, no one — are always singular.

ACT Tip: The always-singular indefinite pronouns worth memorizing: each, every, either, neither, anyone, everyone, someone, nobody, no one. All take singular verbs and singular pronouns.

24 Pronoun-antecedent agreement: basic

A pronoun must agree in number and person with the noun it refers to (its antecedent). Singular antecedents take singular pronouns.

ACT Tip: The ACT regularly pairs singular nouns — “a student,” “a company,” “every person” — with the plural pronoun “their.” That’s the trap. Singular antecedents take “his or her” or “its.”

25 Pronoun-antecedent agreement: across clauses

When a pronoun and its antecedent appear in different clauses or sentences, they still have to agree in number. Distance between them is a common source of mistakes.

ACT Tip: When a pronoun opens a sentence, find its antecedent in the previous sentence and check numbers. “The company” is singular — use “its,” not “their.”

26 Vague and ambiguous pronouns

A pronoun is ambiguous when it could logically refer to more than one noun. Rewrite to make clear which noun it represents.

ACT Tip: If you genuinely can’t tell which noun the pronoun refers to, it’s ambiguous — and wrong. “It,” “they,” and “this” are the most common offenders on the ACT.

27 Reflexive pronouns

Reflexive pronouns (myself, yourself, himself, herself, itself, ourselves, themselves) are used when the subject and object are the same person, or for emphasis. They can’t replace ordinary subject or object pronouns.

ACT Tip: If the subject hasn’t appeared earlier in the sentence, a reflexive pronoun is wrong. “Please send questions to myself” — use “me.” “She blamed herself” is right because the subject “she” already appeared.

28 Its / it’s, your / you’re, their / there / they’re

It’s, you’re, and they’re are contractions. Its, your, and their are possessive pronouns that never take apostrophes. “There” is a location word or sentence starter.

ACT Tip: Substitute the full contraction and read it aloud. “The dog wagged it is tail” — wrong, so use “its” without an apostrophe. This test works for all three pairs.

29 Who vs. whom

“Who” is a subject pronoun — it performs the action. “Whom” is an object pronoun — it receives the action or follows a preposition.

ACT Tip: Substitute he/she or him/her. If “he” fits, use “who.” If “him” fits, use “whom.” Prepositions always take object pronouns — so “to whom” is always correct.

30 Commonly confused word pairs: basic

The pairs that appear most: there/their/they’re, its/it’s, your/you’re, past/passed, lead/led, affect/effect, then/than, loose/lose.

ACT Tip: “Affect” is a verb; “effect” is a noun. “Than” is for comparisons; “then” marks time. “Passed” is the past tense of “pass”; “past” is a noun, adjective, or preposition. These appear on nearly every ACT.

31 Commonly confused word pairs: advanced

Less common pairs: allude/elude, elicit/illicit, principal/principle, complement/compliment, stationary/stationery, precede/proceed, adverse/averse.

ACT Tip: “Allude” means to refer to indirectly; “elude” means to escape. “Elicit” means to draw out a response; “illicit” means illegal. Context always reveals the right word — figure out the meaning the sentence needs, then choose.

32 Idiomatically correct prepositions

Many verbs and adjectives pair with specific prepositions by convention: “interested in,” not “interested about”; “different from,” not “different than”; “capable of,” not “capable to.”

ACT Tip: Key pairings to know: “interested in,” “capable of,” “agree with,” “differ from,” “rely on,” “responsible for,” “concerned about.” If a preposition sounds off, trust that instinct.

33 Idiomatic prepositions with verbs: advanced

More complex verb-preposition pairings must also be correct: “long for,” “appeal to,” “account for,” “result in,” “consist of,” “subscribe to,” “abstain from.”

ACT Tip: Read each answer choice aloud in the full sentence. The wrong preposition sounds off to a careful reader. When multiple choices are grammatically possible, the standard idiomatic pairing is correct.

34 Avoiding “would of,” “could of,” “should of”

The correct forms are “would have,” “could have,” and “should have.” “Would of” is a misspelling of the spoken contraction “would’ve” — it’s never correct in writing.

ACT Tip: “Would of gone” is always wrong. Write “would have gone.” “Of” is only ever a preposition — never part of a verb phrase.

35 Double negatives

Using two negative words in the same clause — “don’t have nothing,” “can’t hardly,” “wasn’t never” — creates a double negative, which is always a grammatical error in standard written English.

ACT Tip: Words like “hardly,” “barely,” “scarcely,” and “never” are already negative — they can’t appear with another negative word like “couldn’t” or “don’t.” One negative per clause.

36 Redundancy and wordiness

The ACT tests conciseness as well as correctness. Phrases that repeat the same meaning — “advance planning,” “end result,” “return back,” “close proximity” — are redundant and wrong.

ACT Tip: On the ACT, the shortest grammatically correct answer is usually right. If you can remove a word without changing the meaning, it shouldn’t be there. Watch for “due to the fact that” (use “because”), “at this point in time” (use “now”), and similar bloated phrases.

Part 3: Punctuation (Rules 37–50)

Punctuation questions test your ability to correctly use — and correctly avoid — commas, semicolons, colons, apostrophes, and dashes. The most commonly tested punctuation rules on the ACT are comma placement and apostrophe use.

37 Deleting commas between verb and direct object

Never put a comma between a verb and the word or phrase that directly completes it, or between a subject and its verb.

ACT Tip: A comma right before “that” introducing a noun clause after a verb — delete it. “She decided, to leave” and “He knew, that it was wrong” are both errors. No comma between a verb and what follows it directly.

38 Deleting commas between modifier and modified element

Don’t put a comma between an adjective and the noun it modifies, between an adverb and the adjective it modifies, or between a noun and an essential modifier right after it.

ACT Tip: Try inserting “and” between the adjectives. “A long and red coat” sounds wrong — no comma. “A cold and windy night” sounds fine — coordinate adjectives, so a comma works.

39 Commas in a series

Use commas to separate three or more items in a series. Including the Oxford comma — the comma before the final “and” or “or” — is the clearest choice and the safe convention for ACT prep.

ACT Tip: When in doubt, include the Oxford comma. It’s generally the clearest and safest choice on the ACT.

40 Deleting commas in compound subjects and verbs

No comma between two subjects joined by “and,” and no comma between two verbs sharing the same subject and joined by “and.”

ACT Tip: A comma before “and” is only correct when both sides are full independent clauses, each with its own subject. If the second verb shares the subject of the first, drop the comma.

41 Commas to avoid ambiguity with introductory elements

Use a comma after a long introductory phrase or clause to prevent misreading. For a very short, unambiguous opener, the comma may be optional.

ACT Tip: If the introductory element could attach to the wrong word without a comma, the comma is mandatory. When uncertain, add it.

42 Commas to set off simple parenthetical elements

A word, phrase, or clause that adds non-essential information mid-sentence gets commas on both sides. Remove it and the sentence should still be complete and clear.

ACT Tip: Transitional words like “however,” “therefore,” “moreover,” and “for example” always take commas on both sides when they appear mid-sentence.

43 Commas to set off complex parenthetical elements

Longer interruptive phrases and clauses also need commas on both sides — a matched pair. One comma when two are needed is a trap the ACT uses constantly.

ACT Tip: Both the opening and closing comma must be present. A non-essential clause with only one comma is always wrong — check that the parenthetical is properly closed.

44 Incorrect uses of colons and semicolons

A semicolon joins two independent clauses. A colon must be preceded by a complete independent clause. Neither works before a dependent clause or an isolated phrase.

ACT Tip: Replace the semicolon with a period — if both sides aren’t complete sentences, it’s wrong. For a colon, cover everything before it and check: is that a complete sentence? If not, the colon is wrong.

45 Semicolons to link independent clauses

A semicolon joins two closely related independent clauses without a coordinating conjunction. Think of it as a period that signals a tighter connection between the two ideas.

ACT Tip: A semicolon followed by a transitional word still needs a comma after that word: “The plan failed; however, the team adapted.” If a period wouldn’t work there, neither does a semicolon.

46 Colons to introduce examples or elaborations

A colon introduces a list, explanation, or elaboration. The clause before the colon must be a complete sentence. Never put a colon directly after a verb or preposition.

ACT Tip: Cover everything before the colon. Not a complete sentence? The colon is wrong. “The museum displayed works by” is not a complete sentence, so the colon fails.

47 Apostrophes: singular possession

Add apostrophe + s to any singular noun to show possession, including nouns that end in s.

ACT Tip: For the ACT, write singular possessives with apostrophe + s — including names ending in s: “James’s argument.” The apostrophe always comes before the s. A missing apostrophe is always wrong.

48 Apostrophes: plural possession

For plural nouns ending in s, add only an apostrophe after the s. For irregular plurals not ending in s — children, men, women, people — add apostrophe + s.

ACT Tip: The apostrophe’s position tells you singular or plural. “The student’s essay” = one student. “The students’ essays” = many. Irregular plurals like “children” take ‘s: “the children’s toys.”

49 Apostrophes: never use for plurals

Apostrophes never form the plural of a noun, number, decade, or abbreviation. Just add s (or es) — no apostrophe.

ACT Tip: Apostrophes mark possession or contractions — never plurals. “1990s,” “CEOs,” “PhDs,” “the Smiths” are all correct. Any apostrophe used to form a simple plural is always wrong on the ACT.

50 Commas in complex series with internal punctuation

When list items already contain commas — a city and state, a name and title — use semicolons between the items instead of commas to keep the list readable.

ACT Tip: Any internal comma in a list item is a signal to switch all separators to semicolons. Otherwise readers can’t tell which commas divide items and which ones are inside items.