Definition · Plain-language
Parallel structure in writing
Parallel structure (or parallelism) means using the same grammatical form for all items in a series, list, paired comparison or correlative construction, making sentences clearer and more balanced.
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What parallel structure is and why it matters
Parallel structure is the grammatical principle that items coordinated in a sentence — listed together or compared — should share the same grammatical form. A series of three gerunds, three infinitives, three noun phrases, three clauses — each must match. When forms mix, readers have to pause and re-process: "The study aimed to collect data, analysing patterns, and the results were interpreted" mixes an infinitive (to collect), a gerund (analysing) and a clause (the results were interpreted). The corrected version — "The study aimed to collect data, to analyse patterns, and to interpret the results" — is instantly clearer. Parallel structure is not merely a stylistic preference; it is a marker of analytical clarity and precise thinking that readers of academic and professional documents expect.
Parallel structure in lists and with correlative conjunctions
The most common application of parallelism is in lists: bullet points, numbered steps, and inline lists separated by commas. Every item should start with the same part of speech and continue in the same form. A bullet list that begins "Collecting data", "To analyse patterns", "Interpretation of findings" is faulty; all three should be gerunds (Collecting, Analysing, Interpreting) or infinitives (To collect, To analyse, To interpret). Correlative conjunctions make parallelism especially visible because the two halves of the pair must balance. "Not only did the experiment fail, but it also exposed a design flaw" is parallel (two independent clauses). "Not only failing but also a design flaw was exposed" is not, because a gerund phrase is paired with a clause.
Fixing faulty parallelism
To fix faulty parallelism, identify the coordinating or correlative element, then decide on one grammatical form and apply it consistently. Three-step process: (1) Identify the list or paired comparison. (2) Check that every item shares the same form. (3) Rewrite any mismatched items. Example faulty: "Her responsibilities include managing the team, to coordinate reports, and the budget is overseen by her." Corrected: "Her responsibilities include managing the team, coordinating reports, and overseeing the budget." All three items are now gerund phrases. In comparisons, parallelism also prevents ambiguity: "The second approach is faster than applying the first" is faulty (noun vs gerund phrase); "The second approach is faster than the first" is correct and parallel. Reading the listed items in isolation — skipping the rest of the sentence — quickly reveals non-parallel constructions.
Key facts
At a glance
- Definition: using the same grammatical form for all items in a series, list or paired comparison
- Applies to: lists (inline and bulleted), correlative conjunctions, comparisons, compound predicates
- Rule: if one item is a gerund, all must be gerunds; if one is an infinitive, all must be infinitives
- Correlative pairs: both/and, either/or, neither/nor, not only/but also require balanced elements on each side
- Faulty parallelism: mixing verb forms, nouns and clauses in the same list or paired construction
- Fix: identify the controlling form of the first item and rewrite all others to match
- Academic importance: signals analytical precision and makes complex arguments easier to follow
Common misconceptions
What people often get wrong
Often heard: Parallel structure only applies to long, formal lists.
Actually: Parallelism applies whenever two or more elements are coordinated: a two-item list ("to read and writing" is faulty; "to read and to write" is parallel), paired comparisons, correlative conjunction constructions, and compound predicates. It matters in any sentence, not just enumerated lists.
Often heard: Varying the form of list items makes writing more interesting and varied.
Actually: In informational and academic writing, varied forms in a parallel list create confusion, not variety. Stylistic variety is achieved through sentence length, structure and vocabulary — not by mixing verb forms within a single list.
Often heard: Parallel structure means every sentence in a paragraph must have the same structure.
Actually: Parallelism applies within a coordinated construction — items in a list, a correlative pair, a comparison. It does not mean every sentence must be structurally identical; sentence variety is still encouraged across a paragraph.
Common questions
FAQ
What is parallel structure in grammar?+
Parallel structure (or parallelism) means using the same grammatical form for all items in a coordinated construction — a series, list, paired comparison or correlative conjunction pair. If the first item in a list is a gerund (collecting), all items must be gerunds (analysing, reporting). Parallelism makes sentences clearer, more balanced and easier to read.
What is an example of faulty parallelism?+
Faulty: "The researcher enjoys collecting data, to analyse results, and the writing of reports." The three items mix a gerund (collecting), an infinitive (to analyse) and a noun phrase (the writing of). Corrected: "The researcher enjoys collecting data, analysing results, and writing reports." All three are now gerunds, making the list parallel.
How does parallel structure work with correlative conjunctions?+
Correlative conjunctions (both...and, either...or, neither...nor, not only...but also) require the same grammatical form on each side of the pair. "She is both knowledgeable and hardworking" is parallel (two adjectives). "She is both knowledgeable and works hard" is not (adjective vs clause). Ensure the element that immediately follows each part of the pair is the same type.
Going deeper
