The Common Core, as well as portions of many standardized tests, require students to recognize and improve poorly-constructed sentences. It's important for students to know what problems appear frequently within these sentences in order to improve their chances of scoring well. One common sentence problem involves non-parallel structure.
What Is Parallel Structure in a Sentence or Phrase?
Parallel structure involves using the same pattern of words or the same voice in a list of items or ideas. By using parallel structure, the writer indicates that all of the items in the list are of equal importance. Parallel structure is important in both sentences and phrases.
Examples of Problems with Parallel Structure
Problems with parallel structure usually occur after a coordinating conjunction such as "or" or "and." Most are a result of mixing gerunds and infinitive phrases or mixing active and passive voice.
Mixing Gerunds and Infinitive Phrases
Gerunds are verb forms that end with the letters -ing. Running, jumping, and coding are all gerunds. The following two sentences correctly use gerunds in parallel structure:
Bethany enjoys baking cakes, cookies, and brownies.
She doesn't like washing dishes, ironing clothes, or mopping the floor.
The sentence below is incorrect, however, because it mixes gerunds (baking, making) and an infinitive phrase (to eat out):
Bethany likes to eat out, baking cakes, and making candy.
This sentence contains an unparallel mixture of a gerund and a noun:
She doesn't like washing clothes or housework.
But this sentence contains two gerunds:
She doesn't like washing clothes or doing housework.
Mixing Active and Passive Voice
Writers can correctly use either the active or the passive voice--but mixing the two, especially in a list, is incorrect. In a sentence that uses the active voice, the subject performs an action; in a sentence that uses the passive voice, the action is performed on the subject. For example:
Active voice: Jane ate the donut. (Jane, the subject, acts by eating the donut.)
Passive voice: The donut was eaten by Jane. (The donut, the subject, is acted upon by Jane.)
Both of the above examples are technically correct. But this sentence is incorrect because the active and passive voices are mixed:
The director told the actors that they should get a lot of sleep, that they should not eat too much, and to do some vocal exercises before the show.
A parallel version of this sentence might read:
The director told the actors that they should get a lot of sleep, that they should not eat too much, and that they should do some vocal exercises before the show.
Parallel Structure Problems in Phrases
Parallelism is necessary not only in full sentences but also in phrases, as well:
The British Museum is a wonderful place to see ancient Egyptian art, find beautiful textiles from around the world, and you can explore African artifacts.
This sentence sounds jerky and out of balance, doesn't it? That's because the phrases are not parallel. Now read this:
The British Museum is a wonderful place where you can find ancient Egyptian art, explore African artifacts, and discover beautiful textiles from around the world.
Notice that each phrase has a verb and a direct object. Parallelism is necessary when a series of words, thoughts, or ideas appear in one sentence. If you encounter a sentence that just sounds wrong or clunky, look for conjunctions like and, or, but, and yet to determine whether the sentence is off balance.