Parallel Structure
When two or more items are grammatically equal, present them in similar structures unless there is a deliberate reason not to. Parallelism is about structural correspondence, not repeating every word identically.
Parallel structure uses comparable grammatical forms for elements that have the same role, especially in coordinated words, phrases, clauses, and lists. Matching the forms helps readers see the relationship among the ideas.
Key details
Important caveats
Boundary
Do not force awkward repetition merely to look symmetrical. The goal is a clear grammatical relationship, not mechanical sameness.
Further guidance
Diagnostic
Mark the coordinated items and compare their forms: noun with noun, -ing phrase with -ing phrase, infinitive with infinitive, clause with clause, as the structure requires.
Revision
If one item changes grammatical shape for no reason, revise the set so equivalent ideas use comparable forms.
Worked Example
Less parallel: “The role requires drafting reports, to brief clients, and careful research.” Parallel: “The role requires drafting reports, briefing clients, and conducting careful research.”
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- Sentence Clarity (opens in a new tab)Purdue Online Writing Lab · Explains parallel structure as using similar grammatical construction for coordinated words, phrases or clauses to make relationships clearer.
- Sentence Clarity: Transcript (opens in a new tab)Purdue Online Writing Lab · Provides current examples showing why matched grammatical forms improve clarity and how nonparallel structures can be revised.