Parallelism

In grammar, parallelism is a balance of two or more similar words, phrases, or clauses. The application of parallelism in sentence construction improves writing style and readability. Parallelism may also be known as parallel structure or parallel construction. In English, parallelism of the predicate provides for one of the few structural situations in which the subject for each verb does not need restatement (a common misconception for foreign speakers). See also parallelism (rhetoric).

Compare the following examples:

Lacking parallelism: She likes cooking, jogging, and to read.

Parallel: She likes cooking, jogging, and reading.

In the above example, the first sentence has two gerunds and one infinitive. To make it parallel, the sentence was rewritten with three gerunds instead.

Lacking parallelism: The dog ran across the yard, jumped over the fence, and down the alley he sprinted.

Parallel: The dog ran across the yard, jumped over the fence, and sprinted down the alley.

Lacking parallelism: Corey admires people with integrity and who have character.

Parallel: Corey admires people who have integrity and who have character.

Parallel: Corey admires people who have integrity and character.

Parallel: Corey admires people with integrity and character.

Unskillful writers often violate this principle, from a mistaken belief that they should constantly vary the form of their expressions. It is true that in repeating a statement in order to emphasize it writers may have need to vary its form. But apart from this, writers should follow carefully the principle of parallel construction.

The left-hand version gives the impression that the writer is undecided or timid; he seems unable or afraid to choose one form of expression and hold to it. The right-hand version shows that the writer has at least made his choice and abided by it.

By this principle, an article or a preposition applying to all the members of a series must either be used only before the first term or else be repeated before each term.

Correlative expressions (both, and; not, but; not only, but also; either, or; first, second, third; and the like) should be followed by the same grammatical construction. Many violations of this rule can be corrected by rearranging the sentence.

When making comparisons, the things you compare should be couched in parallel structures whenever that is possible and appropriate.

Parallel structure is really a matter of balance.  Balancing a sentence can be compared to balancing a scale if we pretend that certain words -- and, or, but -- are the balancing points and if we understand that the words being balanced must carry the same "weight" in the sentence.  One part of speech or of a sentence can be balanced only by one (or a series) of the same kind.

Notice that modifiers (like "down by the pier," "with the sunrise," and "of the fisherman") do not affect the balance of the sentences.

This example sentence is unbalanced because "and" divides two different parts of speech.  An "ing" word is used before and,while an infinitive, "to walk," is used after.  To make the sentence parallel, simply use the same part of speech for both ideas.

Here again, the form of the last item, "how to make ropes," doesn't match the other items and seems too heavy.  To balance the sentence, change the form to match as in the parallel example.

This time the sentence is unbalanced because the first two phrases include verbs, "study" and "get," but the last phrase doesn't contain a verb.   To be parallel, each phrase should follow the pattern of the first one in the series.  This can be accomplished by adding a verb to the last phrase.

Parellelism using common connectors

A slightly different parallelism involves the common connectors-- either/or, neither/nor, not only/but also, if/then.  Here, the kind of word or part of a sentence that follows the first connector must be the same as the kind following the second.  Consider the following examples.
 

Here the two prepositional phrases are parallel; they are the same kind of structure.

In this case, the verb "destroyed" cannot balance the noun "homes."  The sentence should be rewritten so that "destroyed" appears before "not only" and so nouns follow both connectors.

Unskillful writers often violate this principle, from a mistaken belief that they should constantly vary the form of their expressions. It is true that in repeating a statement in order to emphasize it writers may have need to vary its form. But apart from this, writers should follow carefully the principle of parallel construction.

The left-hand version gives the impression that the writer is undecided or timid; he seems unable or afraid to choose one form of expression and hold to it. The right-hand version shows that the writer has at least made his choice and abided by it.

By this principle, an article or a preposition applying to all the members of a series must either be used only before the first term or else be repeated before each term.

Correlative expressions (both, and; not, but; not only, but also; either, or; first, second, third; and the like) should be followed by the same grammatical construction. Many violations of this rule can be corrected by rearranging the sentence.

When making comparisons, the things you compare should be couched in parallel structures whenever that is possible and appropriate.

Take a quiz on parallel structures here:

http://grammar.ccc.commnet.edu/grammar/cgi-shl/quiz.pl/parallelism_quiz.htm

Take another quiz on parallel structures here:

http://grammar.ccc.commnet.edu/grammar/quizzes/parallelism2_quiz.htm

Abraham Lincoln's
Gettysburg Address

Fourscore and seven years ago our fathers brought forth on this continent a new nation, conceived in liberty and dedicated to the proposition that all men are created equal.

Now we are engaged in a great civil war, testing whether that nation or any nation so conceived and so dedicated can long endure. We are met on a great battle field of that war . We have come to dedicate a portion of that field , as a final resting place for those who here gave their lives that that nation might live. It is altogether fitting and proper that we should do this.

But, in a larger sense, we can not dedicate — we can not consecrate — we can not hallow — this ground. The brave men, living and dead, who struggled here, have consecrated it, far above our poor power to add or detract. The world will little note, nor long remember, what we say here, but it can never forget what they did here. It is for us the living, rather, to be dedicated here to the unfinished work which they who fought here have thus far so nobly advanced. It is rather for us to be here dedicated to the great task remaining before us — that from these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion — that we here highly resolve that these dead shall not have died in vain — that this nation, under God, shall have a new birth of freedom — and that government of the people, by the people, for the people, shall not perish from the earth.