Grammar and Usage

Learning Objectives

• Identify the true subject of a sentence even when intervening phrases separate it from the verb
• Apply subject-verb agreement rules for compound subjects, collective nouns, indefinite pronouns, and inverted structures
• Choose correct pronoun case (subjective, objective, possessive) based on grammatical function
• Ensure pronouns have clear, unambiguous antecedents and match their antecedents in number and gender
• Maintain consistent verb tense within and across sentences, shifting tense only when logic requires it
• Recognize and correct irregular verb forms
• Identify and correct dangling, misplaced, and squinting modifiers
• Apply comparative and superlative forms correctly (more vs. most, -er vs. -est)
• Choose correctly between frequently confused word pairs (affect/effect, fewer/less, good/well, who/whom, lay/lie)
• Recognize idiom errors and select grammatically standard preposition-word combinations
• Apply parallel structure to lists, comparisons, and correlative conjunctions

High-Yield Concepts

Subject-Verb Agreement

Subject-verb agreement is the most frequently tested grammar topic on the ACT. The rule is simple -- singular subjects take singular verbs, plural subjects take plural verbs -- but the ACT constructs sentences that obscure the true subject.

The most common ACT trap is placing a plural noun immediately before a singular verb, separated from the true singular subject by a prepositional phrase. Always locate the true subject by mentally crossing out everything between the subject and verb.

Pronoun Case and Agreement

Pronoun case determines which form a pronoun takes based on its grammatical role. Subjective pronouns (I, he, she, we, they, who) serve as subjects. Objective pronouns (me, him, her, us, them, whom) serve as objects of verbs or prepositions. Possessive pronouns (my/mine, his, her/hers, its, our/ours, their/theirs, whose) show ownership.

The most common ACT case error involves compound structures. To identify the correct form in "She gave it to [he/him] and I/me," remove the other person: "She gave it to him" and "She gave it to me." Object of preposition requires objective case: him and me.

Pronoun-antecedent agreement requires pronouns to match their antecedents in number. Indefinite pronouns (everyone, someone, anyone, each, neither, either) are singular and require singular pronouns. Collective nouns are typically singular.

Verb Tense, Form, and Modifier Placement

Verb tense consistency is tested throughout the Grammar and Usage unit. Tense should not shift within a narrative without a logical reason. Past tense passages should maintain past tense; present tense discussions should maintain present tense. The ACT often presents answer choices where three options correctly maintain tense and one introduces an unjustified tense shift.

Modifier errors are among the ACT's most tested usage errors. A dangling modifier introduces a participial phrase that does not logically modify the sentence's true subject. A misplaced modifier is positioned far from the word it modifies, creating ambiguity. The correction always involves placing the modifier directly next to the noun or pronoun it describes.

Study Strategy

Begin with subject-verb agreement, as it is the single highest-frequency topic in this unit. Focus specifically on intervening phrases, indefinite pronouns, and compound subjects -- the three patterns the ACT tests most consistently.

Next, study pronoun case and pronoun-antecedent agreement together. Both involve matching pronoun form to a grammatical requirement. The compound structure trick (isolate the pronoun from its partner) solves most case questions, and the indefinite pronoun list (everyone, each, either, neither, anyone, someone = singular) solves most agreement questions.

Then work through verb issues as a group: tense consistency, irregular verbs, and verb form. These are largely rule-and-recognition exercises that reward familiarity with common irregular forms (lie/lay, rise/raise, bring/brought, see/saw/seen).

After verbs, study modifier placement (dangling, misplaced, squinting), which requires understanding the logical relationship between a modifying phrase and the noun it modifies. Practice by identifying the implied actor in an introductory participial phrase and verifying it matches the sentence's subject.

Work through frequently confused word pairs (affect/effect, fewer/less, good/well, who/whom, their/there/they're, between/among, amount/number) as a dedicated vocabulary-and-grammar review. Then cover logical comparisons, parallel structure, and idioms as a final cluster, as these topics blend grammar with rhetorical precision.

Common Mistakes

• Agreeing the verb with the nearest noun rather than the true grammatical subject
• Using "their" or "they" to refer to singular indefinite pronouns like "everyone" or "each"
• Choosing "I" over "me" in compound object constructions because "I" sounds more formal
• Confusing "who" and "whom" by ignoring function; "who" is always subjective, "whom" is always objective
• Shifting verb tense without a logical reason, especially switching from past to present mid-passage
• Using regular past tense forms for irregular verbs (runned, goed, bringed)
• Writing modifying phrases that dangle by attaching to the wrong noun in the main clause
• Confusing "affect" (usually a verb meaning to influence) with "effect" (usually a noun meaning result)
• Using "less" with countable nouns instead of "fewer" (fewer students, not less students)
• Treating collective nouns as plural when they act as a unified entity
• Making illogical comparisons ("Her score was higher than the other students" compares a score to students rather than to their scores)

Exam Tips

• For subject-verb agreement, cross out all prepositional phrases and relative clauses mentally, then check the stripped-down subject and verb
• For pronoun case in compound structures, test each pronoun individually by removing its partner
• When a sentence opens with an -ing or -ed participial phrase, verify that the sentence's subject is the actor performing that action
• For frequently confused words, build a quick decision tree: "affect" is almost always a verb; "effect" is almost always a noun
• "Who vs. whom": substitute "he" vs. "him" -- if "he" fits, use "who"; if "him" fits, use "whom"
• For verb tense questions, note the tense of the surrounding paragraph before selecting an answer
• Modifier questions often have a "correct" answer that simply reorders the sentence without changing the meaning; look for the option that places the modifying phrase immediately next to what it modifies
• Parallel structure questions require all items in a list or comparison to share the same grammatical form; scan all items before selecting
• Idiom errors typically involve incorrect prepositions; if a phrase sounds unnatural with the given preposition, check alternatives
• "NO CHANGE" is a legitimate answer even when something sounds odd; verify that the supposedly correct alternative is actually more standard before changing