ACT Conventions of Standard English: Grammar & Punctuation

Conventions of Standard English is the largest category in ACT English, covering roughly 40–42 of 75 questions. These are mechanical grammar questions with a correct answer derivable from grammatical rules — unlike rhetorical-skills questions, context matters less. The major subtypes: sentence boundaries (fragments and run-ons), punctuation (commas, semicolons, colons, apostrophes, dashes), subject-verb agreement, pronoun case and agreement, modifier placement, and verb tense consistency.

Because this category is rule-based, it is the highest-leverage area to study. Learning 8–10 core grammar rules can unlock 30+ correct answers on test day.

Commas: use a comma + coordinating conjunction (FANBOYS: for, and, nor, but, or, yet, so) to join two independent clauses. A comma alone between two independent clauses is a comma splice — always wrong. Use a semicolon to join two independent clauses without a conjunction.

Apostrophes: use 's for possession (the dog's bowl), s' for plural possession (the dogs' bowl), and never for a simple plural. "It's" = it is; "its" = possessive.

Subject-verb agreement: find the real subject by crossing out prepositional phrases. "The results of the study was published" is wrong — the subject is "results," not "study."

Fragments: every sentence needs a subject and a verb that together express a complete thought. Participial phrases beginning with -ing do not count as complete verbs.

Using a comma where a semicolon is needed is the most common punctuation error on the ACT. If both sides of the punctuation mark are independent clauses and there's no FANBOYS conjunction, use a semicolon (or a period, or a dash — not a comma alone).

Apostrophe confusion on pronouns is persistently common. Possessive pronouns (its, their, whose, your) never take apostrophes. Only contractions do (it's, they're, who's, you're).

Misidentifying the subject because of an intervening phrase: "The collection of rare coins were donated" — the subject is "collection" (singular), so it should be "was donated."

Make a rule card for the 8 most common conventions errors: comma splices, apostrophes, subject-verb agreement, pronoun agreement, dangling modifiers, semicolons, colons, and parallel structure. Review it before every practice session until the rules are automatic.

On test day, when a Conventions question stumps you, read the answer choices to identify the grammatical dimension being tested (is this about commas, apostrophes, or word choice?), then apply the relevant rule. Don't try to "hear" the correct answer — rules beat intuition on conventions.