Parallel structure
Items in a list or a pair must have the same grammatical form.
Updated October 29, 2026
The rule
If the first item is an -ing word, the rest are too: hiking, swimming and fishing. If the first is "to" plus a verb, keep that form, or drop "to" from all of them after the first.
Pairs such as not only ... but also, both ... and, and either ... or need the same kind of words after each part.
Examples
She likes hiking, swimming, and to fish.She likes hiking, swimming, and fishing.He is not only smart but also has kindness.He is not only smart but also kind.
Quick test: Line the items up in a column. They should look like the same kind of word.
Try it: find the mistake
The mistake in each sentence is highlighted. Say the fix out loud, then open the answer.
I like to swim, to run and biking.
I like to swim, to run and to bike.
The list starts with "to swim, to run", so the last item must be "to bike".
The job requires patience, skill and being careful.
The job requires patience, skill and care.
The other items are nouns (patience, skill), so the last one should be a noun too: care.
She would rather read a book than watching TV.
She would rather read a book than watch TV.
"Would rather read ... than watch": both verbs take the same form.
My weekend plans are cleaning my room, visiting Grandma and to finish my project.
My weekend plans are cleaning my room, visiting Grandma and finishing my project.
The other plans are -ing words, so this one is too: finishing.
Where this rule is tested
Questions people ask
What is the rule for parallel structure?
Items in a list or a pair must have the same grammatical form. If the first item is an -ing word, the rest are too: hiking, swimming and fishing. If the first is "to" plus a verb, keep that form, or drop "to" from all of them after the first.
How can I check my parallel structure quickly?
Line the items up in a column. They should look like the same kind of word.
Where can I practice this for free?
In Owl Test Prep's Daily Grammar Fix: one sentence a day for everyone, plus practice sets of five on this rule. It is free, with no account.