Parallel Sentence Structures

Parallelism in sentences refers to matching grammatical structures. Elements in a sentence that have the same function or express similar ideas should be grammatically parallel, or grammatically matched. Parallelism is used as a rhetorical and stylistic device in literature, speeches, advertising, and popular songs.

I sighed as a lover, I obeyed as a son—Edward Gibbon
Reading is to the mind what exercise is to the body—Joseph Addison
Ask not what your country can do for you; ask what you can do for your country—John F. Kennedy

Parallelism lends balance and grace to writing. It can make a sentence memorable. Even in prose not destined for greatness, parallelism is important.

Faulty parallelism

A failure to create grammatically parallel structures when they are appropriate is referred to as faulty parallelism. In the following examples, note the difference between correct parallel structure and faulty parallelism.

What counts isn't how you look but how you behave.
NOT What counts isn't how you look but your behavior.
The president promised to reform health care, preserve social security, and balance the budget.
NOT The president promised to reform health care, preserve social security, and a balanced budget.

Check for faulty parallelism in your own writing. Nouns should be parallel with nouns, participles with participles, gerunds with gerunds, infinitives with infinitives, clauses with clauses, and so on. Be especially vigilant in the following situations.

Parallel structure in a series

When your sentence includes a series, make sure you have not used different grammatical structures for the items.

He described skiing in the Alps, swimming in the Adriatic, and the drive across the Sahara Desert. (faulty parallelism)
He described skiing in the Alps, swimming in the Adriatic, and driving across the Sahara Desert. (parallel)

In the parallel version, all the elements in the series begin with gerunds: skiing, swimming, driving. In the nonparallel version, the final element is a noun but not a gerund.

The elements would remain parallel even if the phrases following the gerunds were changed or omitted. The length of the items in the series does not affect the parallel structure.

He described skiing, swimming in the Adriatic, and driving across the desert. (parallel)

It doesn't matter what grammatical structure you choose for your series as long as you keep it consistent.

Elaine liked to have a beer, exchange stories with her friends, and watch the men walk by. (parallel)
Elaine liked having a beer, exchanging stories with her friends, and watching the men walk by. (parallel)

When you use words such as to, a, an, his, her, or their with items in a series, you can use the word with the first item, thus having it apply to all the items; or you can repeat it with each item. If you choose to repeat it, you must do so with all the items, not just some of them.

He liked their courage, stamina, and style. (parallel)
He liked their courage, their stamina, and their style. (parallel)
He liked their courage, stamina, and their style. (not parallel)

She saw a van, car, and bicycle collide. (parallel)
She saw a van, a car, and a bicycle collide. (parallel)
She saw a van, a car, and bicycle collide. (not parallel)

When you are comparing items in a sentence, obviously parallelism will be important. Make sure that the elements you are comparing or contrasting are grammatically parallel.

He spoke more of being ambassador than of being president.
NOT He spoke more of his term as ambassador than being president.

The schools in the rural area are smaller than the schools in the inner city.
NOT The schools in the rural area are smaller than the inner city.

In the second sentence, schools are being contrasted to the inner city. What the writer wants to contrast are schools in the rural area with schools in the inner city.

In antithetical constructions, something is true of one thing but not another. But not and rather than are used to set up these constructions. As with comparisons, both parts of an antithetical construction should be parallel.

The administration approved the student's right to drop the class but not to meet with the professor.
NOT The administration approved the student's right to drop the class but not meeting with the professor.

The committee chose to postpone the motion rather than to vote on it.
NOT The committee chose to postpone the motion rather than voting on it.

Parallel structure with correlative conjunctions

Errors in parallel structure often occur with correlative conjunctions: either …or; neither …nor; both …and; not only …but also; whether …or. The sentence structure following the second half of the correlative conjunction should mirror the sentence structure following the first half.

The scientists disputed not only the newspaper article but also the university's official statement. (parallel: phrase with phrase)
The scientists disputed not only the newspaper article but also they disputed the university's official statement. (faulty parallelism: phrase with clause)

Either I like the job or I don't like it. (parallel: clause with clause)
Either I like the job or I don't. (parallel: clause with clause)
Either I like the job or not. (faulty parallelism: clause with adverb)

I have neither the patience nor the time to complete the assignment. (parallel: noun phrase with noun phrase)
I have neither the patience to complete the assignment nor do I have the time complete it. (faulty parallelism: phrase with clause)

Be sure that any element you want to repeat appears after the first half of the correlative conjunction. Look at the position of as in the following examples. In the second sentence, as appears before either and is repeated after or, which makes the construction not parallel.

They acted either as individual citizens or as members of the committee.
NOT They acted as either individual citizens or as members of the committee.

In the following example, the last sentence, we expected appears before the first half of the correlative conjunction and should not be repeated after the second half.

We expected not only to be late but also to be exhausted.
OR We expected to be not only late but also exhausted. (better)
BUT NOT We expected not only to be late but also we expected to be exhausted.

Parallel structure with verbs

When you have more than one verb in a sentence, be sure to make the verbs parallel by not shifting tenses unnecessarily. Also, don't shift from an active to a passive verb.

Kate prepared the speech on the plane and delivered it at the conference. (parallel: both verbs are active)
Kate prepared the speech on the plane, and it was delivered by her at the conference. (faulty parallelism: active verb followed by passive verb)

Sometimes sentences use a single verb form with two helping verbs. Look at the following example.

Robert has in the past and will in the future continue to support the measure. (incorrect)

To support belongs with will continue, but not with has. If you read the sentence without and will in the future continue, you will see this: Robert has in the past to support the measure. Rewrite the sentence to include a participial form for has.

Robert has in the past supported, and will in the future continue to support, the measure.
OR Robert has supported the measure in the past, and he will continue to support it in the future.