Faulty Parallelism

Parallelism in a sentence refers to a series of two or more words, phrases, or clauses that are similar in form or that follow the same pattern. Faulty parallelism occurs when this pattern is broken by one of the elements in the sentence. The result is a sentence that is jarring to the reader:

Negotiations need to happen and common ground must be found.

Notice how the sentence runs more smoothly if both parts are put in similar form:

Both sides must negotiate and must find common ground.

Such structures in a sentence create pleasing rhythms for the reader. A parallel sentence shifts smoothly from point to point, item to item. Faulty parallelism has an effect similar to changing gears without using the clutch. In order to avoid sentences that grate on the ear and awkwardly shift grammatical form, apply the following principles:

Put items in a series or list in parallel form

When you have a series of items in a sentence, whether single words or phrases, they need to be in similar form. The most common type of faulty parallelism occurs with the use of the infinitive, the to form of the verb, and with -ing words in a series.

The activities carried out included conducting strategic capability planning, recruitment of forces personnel, and managing the defence services program.

Each phrase in this sentence needs to begin with an -ing word in order for the sentence to flow smoothly:

The activities carried out included conducting strategic capability planning, recruiting forces personnel, and managing the defence program.

Put paired ideas in parallel form

When two ideas are linked in a single sentence with an and, but, or so, they are more effectively paired if you use parallel forms for each clause:

	Reading the novel was a pleasure but to write the essay was agony.
	Reading the novel was a pleasure but writing the essay was agony.

Similarly, in adjoining sentences, parallel phrases tend to make your point more evident and forceful:

Air Forces tend to worship at the altar of technology, regardless of national origin. Armies, on the other hand, tend to emphasize the soldier over technology.

The "tend to" phrase sets up the pleasing parallelism here.

Use parallel forms with correlative conjunctions

The constructions either . . . or, neither . . . nor, not only . . . but also, and both . . . and (see the "Parts of Speech" section under correlative conjunctions) must always be used with phrases and clauses that are in parallel form:

	The vast scale of this challenge gave great scope both for grand success and failing miserably.
	The vast scale of this challenge gave great scope both for grand success and for grand failure.

The two "for grand" phrases after both and and create balance in this sentence and give emphasis to the writer's point.