Parallel structure in grammar: rules, examples and how to fix it

Parallel structure, also called parallelism or parallel construction, means giving ideas of equal weight the same grammatical form. “She likes hiking, swimming and to ride a bike” breaks the pattern: two -ing words, then an infinitive. “She likes hiking, swimming and cycling” keeps it: three -ing words. The rule applies wherever ideas are joined: in lists, in pairs linked by and, but or or, after correlatives such as either…or, and in comparisons.

William Strunk Jr. made it a rule in The Elements of Style (1918): “Express co-ordinate ideas in similar form.” His reason still holds: “The likeness of form enables the reader to recognize more readily the likeness of content and function.” A parallel sentence tells the reader which ideas belong together before they have finished reading it.

Parallel structure at a glance

The four rules of parallel structure

1. Items in a series

Every item in a list of three or more takes the same form. Pick the form of the item that is hardest to change, and rewrite the others to match it.

• Nouns: The kit includes a tent, a stove and two sleeping bags.
• -ing words: Her weekends were for climbing, reading and sleeping late.
• Infinitives: The goal is to cut costs, to keep every store open and to avoid layoffs.
• Verbs in one tense: He checked the locks, turned off the lights and went to bed.
• Clauses: We know what happened, when it happened and who was there.

Words that introduce the items, such as to, the, a, by, in and that, follow the same rule. Use the word before every item or only before the first: “to plan, budget and hire” or “to plan, to budget and to hire,” not “to plan, budget and to hire.” Repeating it is the safer choice when the items are long, because each one then starts on its own.

A three-part thesis statement is a series too. If the three reasons don't share a shape, the essay's structure can look lopsided from the first paragraph. The thesis statement examples show the pattern working.

2. Pairs joined by and, but or or

Coordinating conjunctions join equals, so what stands on each side should match.

• The new manager is organized and has a lot of energy. → The new manager is organized and energetic.
• I want a job that pays well and with flexible hours. → I want a job that pays well and offers flexible hours.
• The committee reviewed the bids, and a decision was made on Friday. → The committee reviewed the bids and made a decision on Friday.

The last one mixes active and passive. Keeping both halves active also tells the reader who decided, which the passive voice examples cover in more detail.

3. Correlative conjunctions

Correlatives come in pairs: either…or, neither…nor, both…and, not only…but also, whether…or. Strunk again: correlative expressions “should be followed by the same grammatical construction, that is, virtually, by the same part of speech.” Most fixes mean moving the first half so it sits directly before the words it introduces.

• She not only writes novels but also screenplays. → She writes not only novels but also screenplays.
• The decision was both a relief and it surprised everyone. → The decision was both a relief and a surprise.
• He neither called nor was there an email. → He neither called nor emailed.
• Whether we sign today or waiting until Monday, the price is the same. → Whether we sign today or wait until Monday, the price is the same.

4. Comparisons and contrasts

The words on either side of than, as or rather than should take the same form, and the things compared should be the same kind of thing. A contrast works the same way. Alexander Pope's line from An Essay on Criticism (1711) sets two infinitives side by side and lets a comma stand in for the repeated verb: “To err is human; to forgive, divine.”

• I'd rather walk than taking the bus. → I'd rather walk than take the bus.
• Learning to code is as hard as a foreign language. → Learning to code is as hard as learning a foreign language.
• Rents in Denver are higher than Omaha. → Rents in Denver are higher than those in Omaha.

The last fix is about logic as much as form. Rents can be compared with rents, not with a city.

How to fix faulty parallelism

Faulty parallelism, also called nonparallel structure, has three standard fixes. Change the odd item so it matches the others. Repeat the introducing word so each item can stand on its own. Or, when the items were never really equal, split them into separate groups or sentences.

Two of these are easy to miss. In “I have never and will never vote,” the sentence borrows vote for both halves, but have never needs voted, so the shared word fits only one of them. And without the second that, “the client was angry” can read as the writer's own claim rather than part of what he said.

Parallelism is about function as well as form. “The dog was muddy, hungry and in no mood for a bath” mixes adjectives with a phrase, and it reads fine, because all three describe the dog. What jars is a change of job, as in “muddy, hungry and ran off,” where a list of qualities turns into an action halfway through.

Parallel structure in lists and headings

Bulleted lists, headings, tables of contents, slide titles and numbered steps make faulty parallelism easier to see than a sentence does, because the items sit one above another and any difference stands out. The Google developer documentation style guide puts it in one line: “Use the same syntax/structure for all list items in a given list, if possible.”

• Make every item complete the lead-in. If a list follows “This guide shows you how to,” each item must start with a verb: export a file, share a link, restore a version.
• Start procedure steps with an imperative. Open the file. Select Export. Choose PDF. A step that slips into “The format should be selected” breaks the rhythm and hides who acts. The standard operating procedure template is built this way.
• Give résumé bullets one shape. “Managed a team of six,” “Ran a $2.4 million budget,” “Raised customer satisfaction by 18 percent”: past-tense verb first, then the result. A bullet that starts “Responsible for” breaks the set.
• Keep headings at one level of grammar. All noun phrases or all -ing phrases or all questions, within a level. Note the choice on your style sheet so the next document follows it.

In a long manual or report, ask the Strokes Assistant to review the document for headings and list items that don't match the rest of their set. Leave a deliberate break, like Lincoln's below, as it is.

Parallelism in Lincoln and Kennedy

Parallel structure is grammar, and it is also one of the oldest tools of persuasion. Matching clauses make two ideas sound equally weighed, so the one word that differs carries the argument. American presidential speeches are full of it.

Rhetoric has names for the variations: isocolon for clauses of equal length, tricolon for a set of three, antithesis for opposites in parallel form. The rhetorical devices list covers tricolon, antithesis and chiasmus, with Lincoln's “With malice toward none” and Kennedy's “ask not” line, and the guide to repetition in literature covers parallelism's close relatives, anaphora and epistrophe.

Practice: fix the faulty parallelism

Rewrite each sentence, then check the answers below.

1. The new hire is smart, ambitious and a hard worker.
2. We can either meet on Tuesday or on Thursday we could call.
3. She enjoys cooking, gardening and to paint landscapes.
4. The proposal was rejected not because of its cost but it came too late.
5. Reading the contract is more important than to sign it quickly.
6. The software lets you track hours, sending invoices and reports.
7. He was told to arrive early, to bring ID and that he shouldn't park in the lot.
8. Steps: Download the installer. The installer should be run as an administrator. Restarting your computer.