Items listed in a sentence must have parallel structure. Make sure that similar items in a sentence conform to a single part of speech.

This car is sporty, economical, and goes very fast.

This sentence is incorrect. The words "sporty" and "economical" are adjectives, but "goes very fast" is a verb phrase. This is an error in parallel structure.

This car is sporty, economical, and fast.

This sentence is correct. The three adjectives are in parallel structure.

This car looks sporty, runs economically, and goes very fast.

This sentence is also correct. There is parallel structure among the three verb phrases.

Look at the following sentence and determine whether there is an error in parallelism:

I like reading books, walking my dog, and crossword puzzles.

This sentence is incorrect. The first two items in the list are gerund phrases, but the last item is a compound noun. The structure of this sentence is not parallel.

I like reading books, walking my dog, and doing crossword puzzles.

This sentence is correct. There is parallel structure among the three gerund phrases in the sentence.

Items in a sentence that are connected by correlative conjunctions (e.g., "either/or," "neither/nor," and "not only/but also") must be in parallel structure.

When Sally grows up, she either wants to be an astrophysicist or a sculptor.

This sentence contains an error in parallelism. Look at the words that follow each of the conjunctions:

• either [wants] + [to be] + [an astrophysicist] (verb + infinitive + noun)
• or [a sculptor] (noun)

Restructure the sentence so that each conjunction is followed only by a noun.

When Sally grows up, she wants to be either an astrophysicist or a sculptor.

This sentence is parallel in structure.

• Read Grammar Examples and Celebrity Quotes with errors in parallelism.
• Take these interactive quizzes to test your ability to identify proper parallel structure in a sentence: 1, 2, 3.