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. |
Worked examples
Example 1: a list of three
Problem For the trip, we packed snacks, checked the tires, and we were filling the tank.
- Stack the items: packed snacks, checked the tires, we were filling the tank.
- The first two are past-tense verbs. The third adds we were and an -ing form.
- 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.
- After either comes take the bus, a verb phrase.
- 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
On weekends I like hiking, swimming, and ___.
- riding my bike
- to ride my bike
- I ride my bike
- ride my bike
Show answer
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.
The coach told us to stretch, to drink water, and ___.
- resting
- we should rest
- to rest
- rested
Show answer
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.
She is not only a talented singer but also ___.
- a skilled dancer
- she dances with skill
- dancing with skill
- to dance well
Show answer
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.
Which sentence uses parallel structure?
- The job requires patience, paying attention to detail, and to be funny.
- The job requires being patient, attention to detail, and you should be funny.
- The job requires patience, attention to detail, and a good sense of humor.
- The job requires patience, to pay attention to detail, and humor.
Show answer
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.
Learning to cook is easier than ___.
- to bake
- you bake
- learning to bake
- baking is
Show answer
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, accessed October 1, 2026
- Purdue OWL, Mechanics Introduction, accessed October 1, 2026
