Parallelism is the use of matching grammatical structures for items that serve the same function. When items in a list, parts of a comparison, or elements of a sentence are parallel, the reader processes them as a set — the repeated structure signals that the items are the same kind of thing.
“She likes swimming, hiking, and biking” is parallel. “She likes swimming, to hike, and bikes” is not — the shifted forms (gerund, infinitive, noun) force the reader to reparse each item. The content is the same; the processing cost is different.
Parallelism operates at multiple scales:
- Within sentences — matching items in lists, comparisons, and paired structures. “Not only X but also Y” requires X and Y to have the same form.
- Within paragraphs — matching sentence structures to signal that the sentences are doing the same work. “First, identify the audience. Second, define the task. Third, draft the document.”
- Across sections — matching headings, section structures, or argument patterns. A document whose sections all follow the same pattern (definition → example → guidance) is parallel at the structural level.
In rhetoric, parallelism is a tool of emphasis and rhythm. Martin Luther King Jr.’s “I have a dream” speech repeats the parallel structure to build cumulative power. Winston Churchill’s “We shall fight on the beaches, we shall fight on the landing grounds, we shall fight in the fields” uses parallelism for momentum. The figure of anaphora — repeating the same word or phrase at the beginning of successive clauses — is parallelism as rhetorical device.
In technical writing, parallelism is a usability requirement. A list of steps where some begin with verbs and others with nouns (“Click the button. The settings page. Enter your name.”) confuses the reader. Parallel lists are scannable; nonparallel lists are not.
Related terms
- syntax — parallelism is a syntactic principle
- anaphora — the rhetorical figure of initial repetition
- coherence — parallel structure contributes to overall coherence
- transition — parallel structure can serve a transitional function