When writers join one element to another with and or or, they sometimes cause confusion by failing to make the elements parallel. Here are a few common problems with parallel structure and ways to fix them, based on principles from Claire Kehrwald Cook’s Line by Line: How to Edit Your Own Writing (Houghton Mifflin, 1985).

Mismatched Parts

When one item in a pair is a gerund—the ing form of a verb used as a noun—and the other is not, your reader may have trouble connecting the parts:

Students often focus too much on figuring out their teacher’s preferences and how they can get a good grade.

Does and join figuring out and the how clause or their teacher’s preferences and the how clause? If and joins figuring out and the how clause, you might add a gerund before the how clause to match figuring:

Students often focus too much on figuring out their teacher’s preferences and determining how they can get a good grade.

If and joins their teacher’s preferences and the how clause, you might replace their teacher’s preferences with a clause:

Students often focus too much on what their teacher prefers and how they can get a good grade.

Missing Words

Sometimes the problem is a missing word:

The writer does her best work in libraries that have shared tables or public areas with couches.

In the above sentence it is unclear if the writer does her best work in libraries with one of two configurations (shared tables or public areas with couches) or if the writer prefers to work in one of two places: libraries or public areas.  Adding in before public areas would make clear that the second sense is meant:

The writer does her best work in libraries that have shared tables or in public areas with couches.

Troublesome Trios

When a word can form a pair with either one of two other words, your meaning may be unclear:

The Smiths learned that their neighbor had won the lottery and arranged to throw a party.

In the sentence above, arranged could pair with either learned or had won. If the Smiths did the learning and arranging, you might clarify by adding the pronoun they, corresponding to The Smiths, before arranged:

The Smiths learned that their neighbor had won the lottery, and they arranged to throw a party.

If the neighbor arranged to throw a party, you could add had before arranged to match had won:

The Smiths learned that their neighbor had won the lottery and had arranged to throw a party.

Think you’ve got the hang of parallelism now? Find out by taking our quiz.

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Jennifer Rappaport

Jennifer Rappaport is managing editor of MLA style resources at the Modern Language Association. She received a BA in English and French from Vassar College and an MA in comparative literature from New York University, where she taught expository writing. Before coming to the MLA, she worked as an acquisitions editor at Oxford University Press and as a freelance copyeditor and translator for commercial and academic publishers.