Parallelism, or parallel structure, refers to the balance achieved when parts of a sentence, paragraph, or larger work match in style, voice, tense, and context. All writers must pay careful attention to ensure their writing remains parallel and balanced.
The simplest error in parallelism occurs when adjectives, nouns, or verbs do not remain alike within a sentence: I read books, watch films, and like to listen to music. While the first two clauses are similar, the third breaks the pattern by introducing the qualifying verb like before the active verb listen. An improved version may read: I read books, watch films, and listen to music. Verbs should agree with verbs, adjectives with adjectives, and nouns with nouns. Thus, if a list begins in simple present, it shouldn’t end in continuous present: Prefer I bike, run, and swim to I bike, run, and go swimming. When using prepositional phrases, repeat the preposition if it does not begin each phrase: A government of the people, by the people, for the people.
When an auxiliary verb begins a verb phrase, maintain it throughout the list. Prefer I like to go biking, swimming, and walking to I like to go biking, swimming, and take walks. (A weak writer may be tempted to correct the incorrect version to I like to go biking, swimming, and on walks, which works grammatically but is not parallel—the first two hobbies take the present participle while the last does not.)
Contextual parallelism tends to be harder to spot than grammatical parallelism: The strongman stands six feet tall, weighs three hundred pounds, and pulls a firetruck a hundred yards. Although grammatically correct, the sentence changes context after the conjunction. A potential fix may read: The strongman stands six feet tall and weighs three hundred pounds, and he can pull a firetruck a hundred yards. Keep related clauses and sentences thematically similar to maintain contextual parallel structure.