When two or more elements of the same sentence have a similar structure.
An unclear sentence rambles, drifting among unrelated topics in a haphazard and confusing fashion. Parallelism helps promote balance, emphasis, clarity, and readability. But what is parallelism?
Parallelism is when elements of a sentence "echo" each other because they have similar form or structure. Repeating key words can contribute to unity within an essay. Parallelism can be useful in many situations, but often we know that it will come in handy when we use words that link or contrast items, such as and, or, and but.
Basic Form of Parallelism
Nonparallel: Students spend their time going to classes, studying, working, and they wish they had time for a social life.
Parallel: Students spend their time going to classes, studying, working, and wishing for a social life.
Nonparallel: High-school students hope for short school days, or four-day weeks would be great, too.
Parallel: High-school students hope for short school days or four-day weeks.
Using Articles with Parallelism
Parallelism requires that an article (a, an, or the) or a preposition applying to all items in a list either appear before the first item only or be repeated before each item. Here are a few examples of the rule in action:
Nonparallel: We can pay with a mark, a yen, buck, or pound.
Parallel: We can pay with a mark, a yen, a buck, or a pound.
Nonparallel: I went to the store on Monday, Wednesday, and on Friday.
Parallel: I went to the store on Monday, Wednesday, and Friday.
Prepositions in Parallelism
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. Here are a few examples of the rule in action:
Nonparallel: His speech was marked by disagreement and scorn for his opponent's position.
Parallel: His speech was marked by disagreement with and scorn for his opponent's position.
Nonparallel: This is a time not for words but action.
Parallel: This is a time not for words but for action.
Correlative expressions are words that tend to show up in pairs. 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. Here are a few examples of the rule in action:
Nonparallel: Either you must grant her request or incur her ill will.
Parallel: You must either grant her request or incur her ill will.
Nonparallel: My objections are first, the injustice of the measure, and second, that it is unconstitutional.
Parallel: My objections are first, that the measure is unjust, and second, that it is unconstitutional.
In some instances, you must figure out which parts of the sentence are parallel in meaning before making them parallel in structure. Here is an example:
Correct: Sal applied himself in his new job, arriving early every day, skipping lunch regularly, and leaving late every night.
In the sentence above, the -ing participlephrases ("arriving early every day," "skipping lunch regularly," and "leaving late every night") are parallel. The main clause—"applied himself in his new job"—is not parallel to these participle phrases. This is because the main verb is "applied." The -ing phrases simply provide additional information about how Sal applied himself. It would distort the meaning to change the sentence to this superficially parallel version:
Incorrect: Sal applied himself in his new job, arrived early every day, skipped lunch regularly, and left late every night.
This version gives all the activities equal emphasis, instead of making the last three activities subordinate to the main activity ("applied himself in his new job").