ACT English: Grammar Rules Overview

The ACT English section tests your ability to edit and refine written passages, making correct grammar, usage, and mechanics second nature under time pressure. Mastering the core rules isn't just about memorizing definitions—it's about developing an editor's eye for clarity and concision within a text's context. Your success hinges on recognizing these rules in action and applying them swiftly to choose the best revision from the answer choices provided.

Foundational Rule: Subject-Verb Agreement

At its core, subject-verb agreement means that a singular subject requires a singular verb form, and a plural subject requires a plural verb form. On the ACT, the test makers create distance between the subject and verb to make errors harder to spot. You must mentally ignore interrupting prepositional phrases or clauses to find the true subject.

Example: The collection of rare coins are on display.

The subject is "collection," which is singular. The prepositional phrase "of rare coins" does not affect the verb. The correct verb is is.

Compound subjects connected by "and" are typically plural. However, subjects connected by "or" or "nor" follow the noun closest to the verb (the proximity rule). Collective nouns (e.g., team, family, group) are usually singular in American English. A crucial ACT strategy is to always identify the subject before looking at the verb in the answer choices.

Pronoun Clarity and Agreement

Pronouns must agree with their antecedents (the nouns they replace) in number and gender. A singular antecedent requires a singular pronoun (he, she, it). A common trap involves indefinite pronouns like everyone, someone, each, and anybody, which are always singular. The phrase "everyone...they" is incorrect on the ACT.

Example: Each of the players prepared their equipment.

The antecedent is the singular "Each," so the correct pronoun is his or her (or a structurally revised sentence to avoid the issue).

Furthermore, pronouns must be unambiguous. If a sentence has two possible antecedents, it is incorrect. Pronouns also have specific cases: subjective (I, you, he, she, it, we, they), objective (me, you, him, her, it, us, them), and possessive (my, your, his, her, its, our, their). Use the subjective case for subjects and the objective case for objects. A frequent test point is pronoun comparisons, as in "She is taller than I [am]" versus "He helped her more than [he helped] me."

Consistency in Verb Tense and Form

Verb tense indicates the time of an action. The primary ACT rule is consistency. Unless a logical shift in time is required, verb tenses should remain consistent within a sentence and paragraph. Be wary of unnecessary shifts between past, present, and future tense. Pay special attention to the perfect tenses (has/have/had + past participle), which are used to show an action completed before another point in time.

Incorrect: After he finished his essay, he goes to the library.

Correct: After he finished his essay, he went to the library.

Also, ensure verbs are in their proper forms. Irregular verbs are a favorite testing ground. Know the principal parts of common irregular verbs (e.g., sing/sang/sung, write/wrote/written, swim/swam/swum). The past participle is the form used with helping verbs like "has," "have," or "had." Using "had wrote" is a definitive error.

Correct Use of Modifiers: Adjectives and Adverbs

Adjectives modify nouns and pronouns, while adverbs modify verbs, adjectives, or other adverbs. The most common error is using an adjective where an adverb is needed, particularly with sense verbs (feel, look, smell, sound, taste) and verbs of being. Remember: if the word describes an action, it likely needs an adverb ending in -ly.

Incorrect: The team played real well.

Correct: The team played really well. ("Really" modifies the adverb "well.")

Correct: I feel bad. (Here, "bad" is an adjective modifying "I," describing a state of being, not the action of feeling.)

Additionally, modifiers must be placed as close as possible to the word they modify to avoid confusion. A misplaced modifier appears to describe the wrong noun, while a dangling modifier has nothing logical to modify in the sentence.

Dangling: After studying for hours, the test seemed easier. (The test didn't study.)

Correct: After studying for hours, I found the test easier.

Comparative and Superlative Forms

Use the comparative form (-er or more) to compare two items. Use the superlative form (-est or most) to compare three or more items. The ACT will test the logic of this distinction and the correct formation of these modifiers.

Incorrect: This is the better of the three options.

Correct: This is the best of the three options. (Three items requires the superlative.)

For one- or two-syllable adjectives, typically add -er or -est (fast, faster, fastest). For longer adjectives, use more or most (beautiful, more beautiful, most beautiful). Never use both forms together (e.g., "more faster" is always wrong). Be familiar with irregular comparatives and superlatives like good/better/best and bad/worse/worst.

Mastering Idiomatic Expression and Word Choice

Idiomatic expressions are common phrases whose meanings cannot be deduced from the individual words. The ACT tests standard prepositional idioms (e.g., agree with a person, agree to a plan, agree on a term) and conventional word pairings. There is no rule to memorize; exposure and practice are key.

Common error categories include:

• Preposition Use: suspicious of, different from (or different than, though from is often preferred), capable of.
• Correlative Conjunctions: These must be used in proper pairs: not only...but also, either...or, neither...nor, both...and.
• Frequently Confused Words: The ACT loves to test homophones and near-homophones. You must know the difference between its (possessive) and it's (contraction for "it is"), their/there/they're, then/than, affect/effect, and who/whom.

Common Pitfalls

1. The "Sound Right" Trap: In conversation, we often use grammar that is technically incorrect. The ACT tests formal written English. Don't trust your ear alone; apply the specific rules. For example, "The data is convincing" may sound fine, but "data" is technically a plural noun (singular: datum), so in very formal contexts, "The data are convincing" could be correct. The passage will give you clues.

1. Its vs. It's: This is perhaps the most frequently tested punctuation/word choice issue. Its is a possessive pronoun (like his or her). It's is a contraction for "it is" or "it has." In every answer choice containing one of these, check if you can substitute "it is." If you can, use it's; if not, use its.

1. Unnecessary Commas with Essential Clauses: Do not use commas to set off a clause that is essential to the meaning of the sentence (a restrictive clause). Use commas only for non-essential (non-restrictive) clauses.

• Essential (No Commas): The book that I borrowed from you is excellent. (Specifies which book.)
• Non-Essential (Use Commas): War and Peace, which I borrowed from you, is a long book. (Adds extra information.)

1. Faulty Comparisons: Comparisons must be logical and parallel. You must compare like things. Adding other or else is often necessary to avoid comparing something to itself.

• Illogical: Chicago's population is larger than any city in Illinois. (This implies Chicago is larger than itself, as it is a city in Illinois.)
• Logical: Chicago's population is larger than that of any other city in Illinois.

Summary

• Isolate the Subject and Verb: Ignore interrupting phrases to ensure subject-verb agreement. Singular subjects need singular verbs; plural subjects need plural verbs.
• Track the Antecedent: Every pronoun must agree in number and gender with a clear, single antecedent. Indefinite pronouns like everyone are singular.
• Maintain Tense Consistency: Keep verb tenses consistent within a narrative unless a shift in time is logically required. Know your irregular verb forms.
• Modify Precisely: Use adjectives for nouns and adverbs for verbs, adjectives, or other adverbs. Ensure modifiers are placed next to the word they describe to avoid confusion.
• Compare Correctly: Use the comparative (-er, more) for two items and the superlative (-est, most) for three or more. Avoid double comparisons.
• Know the Idioms: Memorize common idiomatic expressions and prepositional pairings. Learn the distinctions between frequently confused words like its/it's and affect/effect.