Skidmore Guide to Writing Index
Parallel construction means that words or phrases are written in the same form. If one phrase in a list begins with "of," then other phrases should, too. If one phrase uses the verb form ending in "ing," then other phrases should, too. Here is an example of mismatched sentence parts:
I like skiing, ice skating, and to hike.
Here we have two "ing" verb forms and one infinitive ("to hike"). By using matched parts, we can improve the parallelism:
I like to ski, ice skate, and hike.
I like skiing, ice skating, and hiking.