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Parallel Structure: Meaning, Rules, and Examples

  • 6 min read

Parallel Structure In One Line

Parallel structure means ideas that sit side-by-side in a sentence keep the same grammatical shape (word form, phrase type, or clause pattern). Source-1✅

✅ Parallel

The course covers reading, writing, and editing.

❌ Not Parallel

The course covers reading, writing, and to edit.

In the first line, everything is an -ing form. In the second, the last item switches to an infinitive.

Parallel structure (also called parallelism) is a clarity tool: it lines up sentence parts so the reader can follow the pattern without “re-decoding” each item. It shows which ideas are equal in importance and keeps the rhythm natural. Source-2✅

  • Used In: Lists
  • Used In: Paired Conjunctions
  • Used In: Comparisons
  • Used In: Headings & Outlines
  • Goal: Balanced Meaning

Table of Contents

Meaning
Where It Shows Up
Rules
Lists
Paired Conjunctions
Comparisons
Patterns
Errors Table
FAQ

Meaning and Core Idea

Parallel Structure
Equal ideas are expressed using matching grammar (same part of speech, same phrase type, or same clause pattern).
Parallelism
The broader term for the effect created by parallel structure, especially in series and repeated patterns.
Parallel Construction
Another label for the same concept, common in writing guides and editing notes.

A quick way to spot it: look at the “slots” in a sentence. If one slot holds a noun, the other slots usually hold nouns. If one holds an -ing form, the rest line up as -ing forms. If one is a full clause, the others match as clauses.

Where Parallel Structure Shows Up

Inside Lists and Series

  • Items after a colon
  • Three-or-more verbs in a row
  • Grouped adjectives or adverbs
  • Multiple noun phrases with the same role

Across Paired Structures

  • both … and
  • either … or
  • neither … nor
  • not only … but also
  • whether … or

Another common place: comparisons. When a sentence uses than or as, the parts on both sides tend to read best when they share a matching structure.

Rules That Keep Things Parallel

  1. Match the form: word with word, phrase with phrase, clause with clause.
  2. Match the pattern: if one item starts with -ing, the others follow that -ing pattern.
  3. Match the tense and voice when listing verbs (same time frame, same active/passive choice).
  4. Keep shared words truly shared: place a modifier where it applies cleanly to every item.
  5. Keep pairs aligned: correlative conjunctions sit directly before the matching parts. Source-3✅

Parallel does not mean identical length. One item can be longer, as long as the grammar type stays aligned (all noun phrases, all infinitives, all “that” clauses, and so on).

Lists and Series

Word-Level Parallelism

NounsAdjectivesAdverbs

Parallel: The design values clarity, simplicity, and consistency.

Not parallel: The design values clarity, simplicity, and to be consistent.

Phrase-Level Parallelism

GerundsInfinitives

Parallel: The workshop focuses on building habits, testing ideas, and sharing results.

Not parallel: The workshop focuses on building habits, testing ideas, and to share results.

Clause-Level Parallelism

That-ClausesFull Clauses

Parallel: The report explains that costs increased, that demand shifted, and that timelines changed.

Not parallel: The report explains that costs increased, that demand shifted, and timelines changing.

Parallel Structure With Correlative Conjunctions

Correlative conjunctions come in pairs. They “lock” two parts of a sentence together, so the parts after each half of the pair tend to read best when they share the same structure.

both … and
Both items typically match in form: noun + noun, verb + verb, or phrase + phrase.
either … or
The “either” side and the “or” side line up in grammar shape.
neither … nor
Same idea: two matched pieces, balanced in structure.
not only … but also
Both sides typically mirror each other (two nouns, two adjectives, two clauses, etc.).

Parallel: The update improves not only speed but also stability.

Not parallel: The update improves not only speed but also making it stable.

Parallel Structure In Comparisons Using “Than” and “As”

Comparisons often hinge on than or as. When the two sides match in structure, the comparison stays unambiguous and smooth. Source-4✅

Parallel: Troubleshooting is easier than testing under time pressure.

Not parallel: Troubleshooting is easier than to test under time pressure.

Parallel: The interface is as useful as it is simple.

Not parallel: The interface is as useful as simplicity.

Common Patterns and Fixes

Mixed Verb Forms

  • -ing + -ing + to + verb is a common break.
  • All -ing forms reads as one clean set.
  • All to + verb forms reads as one clean set.

Uneven Modifiers

  • A shared adjective or adverb should fit every item in the series.
  • If it only fits one item, it “tilts” the structure and confuses the set.
  • Balanced modifiers make the whole series feel intentional.

A subtle parallelism break: mixing noun lists with action phrases in the same series. The meaning might still be “guessable,” but the structure feels uneven.

Common Errors Table

Parallel Structure Patterns Side by Side
Trigger Same-Shape Option Mixed-Shape Example Clean Example
List of actions All -ing forms We discussed planning, drafting, and to publish. We discussed planning, drafting, and publishing.
List after a colon All nouns The kit includes: batteries, cables, and to charge devices. The kit includes: batteries, cables, and chargers.
Correlative pair noun + noun The proposal affects not only the schedule but also changing the budget. The proposal affects not only the schedule but also the budget.
Comparison verb phrase + verb phrase Debugging is easier than the explanation. Debugging is easier than explaining the issue.
Clause series All that clauses The memo states that plans shifted, that timelines changed, and costs increasing. The memo states that plans shifted, that timelines changed, and that costs increased.

FAQ

Frequently Asked Questions

Is parallel structure the same as parallelism?

They are closely related. Parallel structure is the grammar pattern in a sentence, while parallelism is the broader effect created by repeated, balanced structures.

Does parallel structure matter outside long lists?

Yes. It shows up in paired conjunctions, comparisons, headings, and any sentence that places two or more ideas at the same level.

Can parallel items be different lengths?

Yes. Length can vary, but the grammatical type should stay consistent, such as all noun phrases, all infinitives, or all clauses.

What is the most common parallelism mistake?

Mixing verb forms in a series, such as combining an -ing form with an infinitive or switching from phrases to clauses mid-list.

Do correlative conjunctions require parallel structure?

They strongly benefit from it. The two halves of the pair typically work best when they introduce matching structures on both sides.