"We think according to nature; we speak according to rules; we act according to custom."
--Francis Bacon
Parallelism is the grammatical similarity between elements in a sentence or in a passage that play similar roles within the sentence or passage. When elements are parallel in meaning and in grammatical function, they also should be parallel in grammatical form.
For example, in She liked reading and writing, the words reading and writing have similar roles because they are both objects of the verb liked, and they are grammatically similar because they are both gerunds. In She liked reading and to write, the gerund reading and the infinitive to write still have similar roles, but they are not grammatically similar; the sentence does not have faulty grammar, since both She liked reading and She liked to write are grammatically correct, but it has faulty parallelism.
Here are some more examples:
Incorrect: Swimming is better exercise than to ski.
Correct: Swimming is better exercise than skiing.
Incorrect: They came on foot, by car, and bicycle.
Correct: They came on foot, by car, and by bicycle.
Incorrect: In spring, in summer, and fall
Correct: In spring, in summer, and in fall
Correct: In spring, summer, and fall
Parallel grammatical constructions are used to express parallel ideas. Use parallel words, phrases, clauses, verbs, and tenses to improve the flow of ideas and heighten effect. Similarity of form helps readers recognize similarity of content or function.
Use parallel construction in lists, bulleted items, or headings. If a list
begins with strong verbs, make the entire list begin with such verbs. The
following example switches from active verbs to passive nouns.
Incorrect:
Add impact to every line.
Explode writing myths.
The simple techniques used to stimulate readers' interest.
Correct:
Add impact to every line.
Explode writing myths.
Use simple techniques to stimulate readers' interest.
Parallel sentence structure also encompasses the concept that two or more sentence elements of equal importance should be expressed similarly. For example,
"The benefits of parallelism are many: an economy of words, a clarification of meaning, a sense of symmetry, and a sense of the equality of each idea in the sentence."--Robert W. Bly
Writers violate parallelism by constructing part of the sentence or passage
in one way and switching to another construction later in the sentence or
passage. This can result when a manuscript is revised but not read. Here is an
example:
Incorrect: Please sign the C-22 form, date it, and it must be sent to
the Coordination Office.
Correct: Please sign the C-22 form, date it, and send it to the
Coordination Office.
Other examples of parallel construction:
The atomic weight of gold is 196.97; silver, 107.87; iron, 55.85; lead,
207.19.
"Ask not what your country can do for you; ask what you can do for your country."--John F. Kennedy
"It was the best of times; it was the worst of times."--A Charles Dickens
". . . government of the people, for the people, and by the people . . ."--Abraham Lincoln
"One small step for man; one giant leap for mankind."--Neil Armstrong
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Last updated: 4/22/2011