ACT English: Parallel Structure in Lists and Compounds

Parallel structure means that items in a list or compound construction must have the same grammatical form. If the first item is a noun, the rest are nouns. If the first is a verb phrase, the rest are verb phrases. If the first is an adjective, the rest are adjectives. The rule applies to lists ("She likes running, swimming, and biking"), compound sentences ("He studied hard and passed the exam"), and any series. The reason: parallel form creates rhythm and clarity. When forms mismatch, the sentence feels clunky and is grammatically wrong. To check parallel structure, list each item vertically and compare their forms. If they don't match, rewrite to make them match.

Wrong: "She enjoys reading, swimming, and to hike." (Two gerunds + one infinitive.) Right: "She enjoys reading, swimming, and hiking." (All gerunds.) Wrong: "The team was organized, prepared, and working hard." (Two adjectives + one verb phrase.) Right: "The team was organized, prepared, and hardworking." (All adjectives after "was.").

Break 1: Mixing gerunds and infinitives in a list. "She wanted to run, jump, and swimming" mixes infinitives and gerunds. Break 2: Mixing nouns and adjectives. "The house was large, comfortable, and a mansion" lists two adjectives and then a noun. Break 3: Mixing active and passive voice in compound actions. "They solved the problem and were celebrated by the community" mixes active (solved) and passive (were celebrated). Break 4: Mixing verb tenses or aspects unnecessarily. "He walked, talked, and was laughing" mixes past simple and past progressive without clear reason. On the ACT, the correct answer will always have parallel form; your job is to spot the mismatched version and eliminate it.

Rapid check: Underline each item in a list and mark its grammatical category. Noun? Verb? Adjective? If they don't all match, you've found the error.

Sentence 1: "The committee valued transparency, efficiency, and working collaboratively." (Nouns + gerund. Fix: "transparency, efficiency, and collaboration.") Sentence 2: "Students should revise their essays, check citations, and proofreading carefully." (Two verb phrases + gerund. Fix: "revise, check, and proofread.") Sentence 3: "The book was entertaining, suspenseful, and a page-turner." (Two adjectives + noun. Fix: "entertaining, suspenseful, and gripping.") Sentence 4: "Athletes train daily, compete weekly, and were improving steadily." (Two simple verb phrases + passive. Fix: "train daily, compete weekly, and improve steadily.") Sentence 5: "She wanted success, happiness, and to be respected." (Two nouns + infinitive phrase. Fix: "success, happiness, and respect.") After fixing, read the corrected version aloud. It should flow smoothly without stuttering.

For each sentence you fix, label the grammatical category of each corrected item to reinforce the pattern.

Parallel structure errors appear on almost every ACT English section, often in the medium-difficulty range. They're worth mastering because they're rule-based, not subjective. Once you internalize the principle, you can spot mismatched forms instantly. Many students lose 2-3 points per test by misunderstanding this rule or not checking lists carefully enough.

This week, identify all lists in your practice passages. Check each item's grammatical form. Develop a reflex: See a list, check for parallel form. By test day, this will be automatic.