Parallel Structure

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Simply stated, Parallel Structure or Parallelism means using the same grammatical structure to express equal ideas in a sequence. This can be done by keeping the same verb tense, by using the same voice (passive or active), or by using the same phrase or clause structure. Overall, parallel structure is all about clarity.

Using Parallel Structure with Coordinating Conjunctions

Make sure that the same grammatical structure is being used on both sides of coordinating conjunctions (and, but, yet, or, nor).

Awkward: I like to bird watch and go golfing on Saturdays
Correct: I like to bird watch and to golf on Saturdays.
Or: I like bird watching and golfing on Saturdays.

Using Parallel Structure with Correlative Conjunctions

Use the same grammatical structure when using correlative conjunctions (either/or, neither/nor, whether/or, not only/but also). Pairs of correlative conjunctions work exclusively together: neither is always used with nor; whether is always used with or, etc.

Awkward: For Joe, buying shoes is neither a walk in the park nor spending a day at the beach
Correct: For Joe, buying shoes is neither a walk in the park nor a day at the beach.
Or: For Joe, buying shoes is neither walking in the park nor spending a day at the beach.

Using Parallel Structure in Lists

Items in a list should also be in the same grammatical structure to show equality among the items in the list.

Awkward: Editorial duties include reading manuscripts, copyediting, and he or she makes suggestions for layout.
Correct: Editorial duties include reading manuscripts, copyediting, and making suggestions for layout.

This same principle can be applied to a vertical list or a list of instructions.

Example:     Effects of rainforest loss:
            ozone depletion
            animal extinction
            habitat deforestation
Or:           Making a sandwich:
1. Select two pieces of bread.
2. Use knife to spread mayo, mustard, or salsa dressing on the bread.
3. Place meat, cheese, and vegetables on bread.
4. Put the bread pieces together and eat.

Using Parallel Structure with Clauses and Phrases

Use the same clausal structure to show realtionships between equal clauses.

Awkward: With parental involvement in PTA and when the administration supports the PTA, after-school programs could be the most successful we’ve seen in years.

In this example the prepositional phrase with parental involvement and the subordinate clause when the administration supports the PTA are not parallel.

One solution would be to create parallel prepositional phrases.

Correct: With the parents’ involvement in the PTA and with the administration’s support of the PTA, after-school programs could be the most successful we’ve seen in years.

The sentence could also be fixed by creating parallel subordinate clauses.

Correct: When parents are involved in the PTA and when the administration supports the PTA, after-school programs could be the most successful we’ve seen in years.

Another way to fix the problem would be to combine the two clauses.

Correct: If the parents and administration are involved in and support the PTA, the after-school programs could be the most successful we’ve seen in years.