What Is Parallel Structure?
Parallel structure (also called parallelism) is the principle that grammatically equal ideas should be expressed in grammatically equal forms. When you list items, compare two things, or pair clauses with coordinating or correlative conjunctions, each element should use the same grammatical form: all nouns, all infinitives, all gerunds, all full clauses.
Examples of parallel structure:
- She likes reading, writing, and hiking. (all gerunds)
- The report was thorough, accurate, and well-organized. (all adjectives)
- We need to hire a developer, train the team, and launch the product. (all infinitives)
Examples of broken parallelism:
- She likes reading, writing, and to hike. (gerund, gerund, infinitive)
- The report was thorough, accurate, and showed good organization. (adjective, adjective, clause)
Why Parallel Structure Matters
Parallelism is not a pedantic rule. It makes sentences easier to process because the reader builds a mental pattern from the first item and expects the others to match. When they do not, the reader must pause to recalibrate. In a list of three items, the third item especially must confirm the pattern set by the first two.
Parallel structure also creates rhythm. Some of the most memorable sentences in English — from political speeches, famous essays, and literature — owe their power to parallelism: equal weight given to equal ideas in equal form.
Parallelism in Lists
The most common place parallelism breaks down is in series of three or more items. The rule: every item in the list must belong to the same grammatical category.
| Faulty | Parallel |
|---|---|
| The job requires attention to detail, communication skills, and being organized. | The job requires attention to detail, strong communication skills, and organizational ability. |
| He enjoys playing chess, cooking Italian food, and to read science fiction. | He enjoys playing chess, cooking Italian food, and reading science fiction. |
| The manager was promoted for her leadership, how she communicated, and dedication. | The manager was promoted for her leadership, communication, and dedication. |
Parallelism with Coordinating Conjunctions
The FANBOYS conjunctions (for, and, nor, but, or, yet, so) join elements of equal rank. Whatever comes before the conjunction should match whatever comes after it in grammatical form.
- Faulty: The proposal was detailed but lacked clarity. (adjective joined to verb phrase)
- Parallel: The proposal was detailed but unclear. (adjective + adjective)
- Faulty: She researched the topic and writing a summary.
- Parallel: She researched the topic and wrote a summary.
Parallelism with Correlative Conjunctions
Correlative conjunctions come in pairs: either...or, neither...nor, both...and, not only...but also, whether...or. The element following the first conjunction must match the element following the second.
| Faulty | Parallel |
|---|---|
| She wants either to transfer or a promotion. | She wants either a transfer or a promotion. |
| The plan is not only cost-effective but also it saves time. | The plan is not only cost-effective but also time-saving. |
| Both the manager and what the team reported were accurate. | Both the manager and the team reported accurately. |
The easiest test: place the two halves of a correlative conjunction side by side and check that the words immediately following each half are grammatically equivalent.
Parallelism in Comparisons
When comparing two things, both sides of the comparison should use the same structure:
- Faulty: Writing a summary is easier than to read the full report.
- Parallel: Writing a summary is easier than reading the full report.
- Faulty: Her approach was more collaborative than what her predecessor did.
- Parallel: Her approach was more collaborative than her predecessor's.
Parallelism in Bullet Points and Headings
Parallel structure is critical in slide decks, reports, resumes, and any document that uses bullet points. All bullets under a single heading should start with the same grammatical form: all action verbs, all noun phrases, all gerunds.
- Faulty bullets: Managing team workflow / Team communication is also important / Reporting to senior leadership
- Parallel bullets: Managing team workflow / Facilitating team communication / Reporting to senior leadership
Resume bullet points are a common place this breaks down. Every bullet describing responsibilities should start with the same verb form (typically past tense for previous roles, present tense for current ones).
How to Spot and Fix Broken Parallelism
Follow these steps when revising:
- Find any list, pair, or series in the sentence.
- Identify the grammatical form of the first item (noun, verb, gerund, infinitive, adjective, clause).
- Check that every other item matches that form.
- If one item is different, either convert it to match the others, or restructure the sentence so all items naturally fit the same form.
If you have written a long sentence with complex lists, reading it aloud helps. A rhythm disruption where one item sounds heavier or longer than the others is often a sign of broken parallelism.
When rewriting sentences for parallel structure, Rephrasely can help you rephrase individual items to match a consistent grammatical form.
Parallelism and Subject-Verb Agreement
Parallel structure interacts with subject-verb agreement when compound subjects are involved. Both the manager and the team member are responsible is parallel. Either the manager or the team members are responsible follows subject-verb agreement rules (verb agrees with the nearest subject). Getting both right simultaneously requires attention to both principles at once.
Frequently Asked Questions
Does every list need to be perfectly parallel?
In formal and academic writing, yes. In casual writing, minor deviations are tolerated if meaning is clear. The more visible the list (a heading, a key argument, a bullet point slide), the more important parallelism becomes. When in doubt, apply it.
What is the difference between parallelism and repetition?
Parallelism is about grammatical form — using the same structure for equivalent ideas. Repetition is about using the same words. A parallel list does not repeat the same words; it uses different words in the same grammatical form. Intentional word repetition for rhetorical effect (We shall fight on the beaches, we shall fight on the landing grounds...) is a different device called anaphora.
Can parallelism be used for emphasis?
Yes. Deliberate parallelism creates emphasis and rhythm. Three parallel items form a rhetorical pattern called a tricolon: veni, vidi, vici (I came, I saw, I conquered). This structure feels complete and authoritative. Used purposefully in persuasive writing, it is a strength. Used accidentally in analytical writing, it can sound overwrought.
Is "not only...but also" always required to have "also"?
No. But also can be shortened to but in informal writing. Not only did she finish the report, but she presented it flawlessly is acceptable. However, dropping also tends to reduce the emphatic effect of the construction. In formal writing, keeping the full pair (not only...but also) is standard.
How does parallelism relate to run-on sentences?
They are independent issues but can co-occur. A run-on sentence joins independent clauses without proper punctuation. A faulty parallelism mismatch within a correctly punctuated sentence is a different error. Fixing both requires identifying clause boundaries (for run-ons) and grammatical categories (for parallelism).