You use parallel structure, or parallelism, when you create a series of words, phrases, clauses, or sentences with the same grammatical form. The pattern created by the series — its parallel structure — emphasizes the similarities or differences among the items, whether things, qualities, actions, or ideas.
My favorite foods are roast beef, apple pie, and linguine with clams.
Louise is charming, witty, intelligent, and talented.
Manuel likes to swim, ride, and run.
Dave likes movies that scare him and books that make him laugh.
See B2 in the Quick Editing Guide for more on editing for parallel structure.
Each series is a perfect parallel construction, composed of equivalent words: nouns in the first example, then adjectives, verbs, and adjective clauses.
| 13a | In a series linked by a coordinating conjunction, keep all elements in the same grammatical form. |
A coordinating conjunction (and, but, for, or, nor, so, yet) cues your readers to expect a parallel structure. Whether your series consists of single words, phrases, or clauses, its parts should balance one another.
For more on coordination, see 14a–14c.
| AWKWARD | The puppies are tiny, clumsily bumping into each other, and cute. |
Two elements in this series are parallel one-word adjectives (tiny, cute), but the third, the verb phrase clumsily bumping, is inconsistent.
| PARALLEL | The puppies are tiny, clumsy, and cute. |
gerund: A form of a verb, ending in -ing, that functions as a noun: Lacey likes playing in the steel band.
infinitive: The base form of a verb, often preceded by to (to go, to play)
Don’t mix verb forms, such as gerunds and infinitives, in a series.
| AWKWARD | Plan a winter vacation if you like skiing and to skate. |
| PARALLEL | Plan a winter vacation if you like skiing and skating. |
| PARALLEL | Plan a winter vacation if you like to ski and to skate. |
In a series of phrases or clauses, be sure that all elements in the series are similar in form, even if they are not similar in length.
| AWKWARD | The fight in the bar takes place after the two lovers have their scene together but before the car chase. [The clause starting with after is not parallel to the phrase starting with before.] |
| PARALLEL | The fight in the bar takes place after the love scene but before the car chase. |
| AWKWARD | You can take the key, or don’t forget to leave it under the mat. [The declarative clause starting with You can is not parallel to the imperative clause starting with don’t forget.] |
| PARALLEL | You can take the key, or you can leave it under the mat. |
| 13b | In a series linked by correlative conjunctions, keep all elements in the same grammatical form |
correlative conjunction: A pair of linking words (such as either/or, not only/but also) that appear separately but work together to join elements of a sentence: Neither his friends nor hers like pizza.
When you use a correlative conjunction, follow each part with a similarly structured word, phrase, or clause.
| AWKWARD | I’m looking forward to either attending Saturday’s wrestling match or to seeing it on closed-circuit TV. [To precedes the first part (to either) but follows the second part (or to).] |
| PARALLEL | I’m looking forward either to attending Saturday’s wrestling match or to seeing it on closed-circuit TV. |
| AWKWARD | Take my advice: try neither to be first nor last in the lunch line. [To be follows the first part but not the second part.] |
| PARALLEL | Take my advice: try to be neither first nor last in the lunch line. |
| 13c | Make the elements in a comparison parallel in form. |
For more on comparisons, see 11a–11d and 11g.
A comparative word such as than or as cues the reader to expect a parallel structure. This makes logical sense: to be compared, two things must resemble each other, and parallel structure emphasizes this resemblance.
| AWKWARD | Philip likes fishing better than to sail. |
| PARALLEL | Philip likes fishing better than sailing. |
| PARALLEL | Philip likes to fish better than to sail. |
| AWKWARD | Maintaining railway lines is as important to the public transportation system as to buy new trains. |
| PARALLEL | Maintaining railway lines is as important to the public transportation system as buying new trains. |
| 13d | Reinforce parallel structure by repeating rather than mixing lead-in words. |
Parallel structures are especially useful when a sentence contains a series of clauses or phrases. For example, try to precede potentially confusing clauses with that, who, when, where, or some other connective, repeating the same connective every time to help readers follow them with ease.
No one in this country needs a government that aids big business at the expense of farmers and workers, that ravages the environment in the name of progress, or that slashes budgets for health and education.
If the same lead-in word won’t work for all elements in a series, try changing the order of the elements to minimize variation.
| AWKWARD | The new school building is large but not very comfortable, and expensive but unattractive. |
| PARALLEL | The new school building is large and expensive, but uncomfortable and unattractive. |