Parallel

A good writer uses parallel structure; that is, he or she puts nouns, verbs, phrases, thoughts, and so on into a similar form. This is done primarily for style: it makes the writing easier to read and in turn, easier for the reader to understand. Often, sentences that seem to be correct but just sound wrong have a lack of parallelism at the core of their problem.

Some examples of parallel and non-parallel structure:

SIMPLE PARALLELISM | WITH ARTICLES | WITH PREPOSITIONS | WITH CORRELATIVES

Parallelism

Nonparallel	Parallel
Students spend their time going to classes,studying, working, and they wish they had time for a social life.	Students spend their time going to classes,studying, working, and wishing for a social life.
By the end of the quarter they're exhausted, irritable, and have learned a lot.	By the end of the quarter they're exhausted, irritable and smarter
BCC students hope for early registration dates, and close-in parking spaces are important, too.	BCC students hope for early registration dates and close-in parking spaces.

The examples on the left give the impression that the writer is undecided or timid, afraid to choose one form of expression and stick with it. The examples on the right give the impression that the writer is at least confident enough to make a choice and keep to it.

WITH ARTICLES | WITH PREPOSITIONS | WITH CORRELATIVE EXPRESSIONS

Parallelism requires that an article (a, an or the) or preposition applying to all members of a series must either appear before the first item only or be repeated before each item.

Nonparallel Parallel

a mark, a yen, buck or pound a mark, a yen, a buck or a pound

on Monday, Wednesday or on Friday on Monday, Wednesday or Friday (on Monday, on Wednesday or on Friday)

SIMPLE PARALLELISM | WITH PREPOSITIONS | WITH CORRELATIVE EXPRESSIONS

Parallelism with Prepositions

Some words require that certain prepositions precede them. When such words appear in parallel structure, it is important to include all of the appropriate prepositions, since the first one may not apply to the whole series of items.

Nonparallel	Parallel
His speech was marked by disagreement and scorn for his opponent's position	His speech was marked by disagreement with and scorn for his opponent's position.

SIMPLE PARALLELISM | WITH ARTICLES | WITH CORRELATIVE EXPRESSIONS

Parallelism with Correlative Expressions

Sentences with correlative expressions (both/and; not/but; not only/but also; either/or; first, second, third) should employ parallel structure as well. Simple rewriting can often remedy errors in these types of sentences.

Nonparallel	Parallel
a time not for words but action	a time not for words but for action
Either you must grant her request or incur her ill will	You must either grant her request or incur her ill will.
My objections are first, the injustice of the measure, and second, that it is unconstitutional.	My objections are first, that the measure is unjust, and second, that it is unconstitutional.

SIMPLE PARALLELISM | WITH ARTICLES | WITH PREPOSITIONS

When you think of a parallel sentence, think of one where all the parts of the sentence that are similar in function are in balance, where they all use the same grammatical form.