The ACT grammar section assesses your knowledge of English grammar and usage. While the specific topics tested can vary from test to test, here are some common grammar areas that frequently appear in the ACT:

1. Punctuation: Questions in this category may test your understanding of proper comma usage, apostrophes, colons, semicolons, dashes, and other punctuation marks. You may be asked to identify errors, determine the appropriate punctuation in a given context, or understand the impact of punctuation on sentence structure and meaning.
2. Sentence Structure: This category covers topics such as subject-verb agreement, verb tenses, parallelism, pronoun agreement, and modifiers. Questions may require you to identify errors in sentence structure, choose the correct verb form, ensure pronoun consistency, or maintain parallel structure within a sentence or passage.
3. Grammar and Usage: This category encompasses a broad range of topics, including verb forms, pronoun usage, adjectives and adverbs, prepositions, conjunctions, idiomatic expressions, and word choice. Questions may test your understanding of correct usage, identify errors in grammar and word usage, or require you to select the most appropriate word or phrase for a given context.
4. Verb Usage: Questions in this category focus specifically on verbs and their usage. You may be tested on verb tense consistency, irregular verb forms, subject-verb agreement, verb mood, or the correct use of auxiliary verbs.
5. Pronouns: This category assesses your knowledge of pronoun usage, including personal pronouns, possessive pronouns, reflexive pronouns, and pronoun antecedent agreement. Questions may require you to identify errors in pronoun usage, choose the correct pronoun form, or ensure clarity and consistency in pronoun references.
6. Agreement: Questions in this category evaluate your understanding of subject-verb agreement, noun-pronoun agreement, and agreement between modifiers and the words they modify. You may be asked to identify errors in agreement, select the appropriate verb or pronoun form, or ensure consistency in number and person.
7. Modifiers: This category focuses on the correct use and placement of adjectives, adverbs, and other modifiers. Questions may test your understanding of modifier placement, comparative and superlative forms, and the proper use of modifiers to convey meaning accurately.
8. Word Choice: Questions in this category assess your ability to choose the most appropriate word or phrase for a given context. You may need to identify errors in word choice, understand connotation and denotation, or select the word or phrase that best expresses the intended meaning.