# Parallel structure

Canonical: https://duckyhelper.com/learn/grammar/parallel-structure/
Updated: 2026-10-01

Parallel structure means using the same grammatical form for parts of a sentence that do the same job. In a list, write hiking, swimming and biking, not hiking, swimming and to bike. In a comparison, match both sides: Learning to cook is easier than learning to bake. After paired words like both...and, either...or and not only...but also, use the same form after each word.

## Where to check for it

| Place | Wrong | Right | Why |
| --- | --- | --- | --- |
| Lists | *I like hiking, swimming, and to ride my bike.* | *I like hiking, swimming, and riding my bike.* | All three items are *-ing* words now. |
| Lists of actions | *The coach told us to stretch, to drink water, and resting.* | *The coach told us to stretch, to drink water, and to rest.* | Each item is a *to* verb. |
| Comparisons | *Learning to cook is easier than to bake.* | *Learning to cook is easier than learning to bake.* | Both sides of *than* use the same form. |
| Paired words | *She is not only a singer but also dances.* | *She is not only a singer but also a dancer.* | After *not only* and *but also*, use the same kind of word: two nouns. |
| Longer items | *The job needs patience, attention to detail, and to be funny.* | *The job needs patience, attention to detail, and a sense of humor.* | Three nouns, so each item is a noun phrase. |

> **Tip: The stack test**
>
> Write each item on its own line under the words that lead into it. Each line should finish the lead-in the same way: *I like / hiking / swimming / riding my bike.*

## Worked examples

**Example 1: a list of three**

Problem: *For the trip, we packed snacks, checked the tires, and we were filling the tank.*

1. Stack the items: *packed snacks*, *checked the tires*, *we were filling the tank*.
2. The first two are past-tense verbs. The third adds *we were* and an *-ing* form.
3. Change the third to match: *filled the tank*.

Answer: *For the trip, we packed snacks, checked the tires, and filled the tank.*

**Example 2: either...or**

Problem: *You can either take the bus or walking is also fine.*

1. After *either* comes *take the bus*, a verb phrase.
2. After *or* must come a verb phrase too: *walk*.

Answer: *You can either take the bus or walk.*

## Common mistakes and fixes

| Mistake | Fix |
| --- | --- |
| Switching from *-ing* to *to* in a list | Pick one form and use it for every item. |
| Adding a new subject to the last item (*and we were*) | Drop the extra words so the last item matches the others. |
| Putting *not only* in the wrong spot | Place *not only* and *but also* right before the matching parts. |
| Comparing a thing to an action | Compare like with like: a noun with a noun, an *-ing* word with an *-ing* word. |

## Practice

**Five parallel structure questions**

1. *On weekends I like hiking, swimming, and ___.*
   A. riding my bike
   B. to ride my bike
   C. I ride my bike
   D. ride my bike

   Answer: riding my bike. The first two items are *-ing* words, so the third must be too. The other choices switch to a *to* form, a full clause, or a plain verb.

2. *The coach told us to stretch, to drink water, and ___.*
   A. resting
   B. we should rest
   C. to rest
   D. rested

   Answer: to rest. The first two items are *to* forms, so the third should be *to rest*. *Resting*, *we should rest* and *rested* break the pattern.

3. *She is not only a talented singer but also ___.*
   A. a skilled dancer
   B. she dances with skill
   C. dancing with skill
   D. to dance well

   Answer: a skilled dancer. After *not only* comes a noun phrase, *a talented singer*, so after *but also* comes a noun phrase too. The other choices use a clause, an *-ing* phrase or a *to* phrase.

4. Which sentence uses parallel structure?
   A. The job requires patience, paying attention to detail, and to be funny.
   B. The job requires being patient, attention to detail, and you should be funny.
   C. The job requires patience, attention to detail, and a good sense of humor.
   D. The job requires patience, to pay attention to detail, and humor.

   Answer: The job requires patience, attention to detail, and a good sense of humor.. All three items are noun phrases. Each other choice mixes nouns with *-ing* phrases, *to* phrases or full clauses.

5. *Learning to cook is easier than ___.*
   A. to bake
   B. you bake
   C. learning to bake
   D. baking is

   Answer: learning to bake. The left side is *Learning to cook*, so the right side should be *learning to bake*. The other choices compare an *-ing* phrase to a different form.

## Frequently asked questions

### Why does parallel structure matter?

It makes sentences easier to read, because the reader can see that the items are equal and follow the same pattern. Teachers mark it as an error in essays, and it shows up in list and comparison questions on tests. It also makes writing sound more confident.

### Do I have to repeat to or the in a list?

You can either use it once at the start or before every item, but be consistent: *to stretch, drink water, and rest* or *to stretch, to drink water, and to rest*. Mixing the two, as in *to stretch, drink water, and to rest*, breaks the pattern.

### Is parallel structure only about lists?

No. It also applies to comparisons with *than* or *as*, to paired words like *both...and* and *either...or*, and to headings and bullet points in a report. Any time two or more parts do the same job, give them the same form.

## Sources

- [Purdue OWL, Improving Sentence Clarity](https://owl.purdue.edu/owl/general_writing/mechanics/sentence_clarity.html), accessed 2026-10-01
- [Purdue OWL, Mechanics Introduction](https://owl.purdue.edu/owl/general_writing/mechanics/index.html), accessed 2026-10-01

## Related

- [Misplaced and dangling modifiers](https://duckyhelper.com/learn/grammar/misplaced-and-dangling-modifiers/)
- [Comma rules](https://duckyhelper.com/learn/grammar/commas/)
- [How to write a thesis statement](https://duckyhelper.com/learn/essay-writing/thesis-statement/)
- [Grammar study guides](https://duckyhelper.com/learn/grammar/)

## Try asking Ducky

- "Check the lists in my essay for parallel structure."
- "My thesis has three reasons. Are they parallel?"
- "Give me five sentences with broken lists to fix."

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