Whether you're comparing ideas or organizing lists, parallel structure improves readability, adds balance, and removes ambiguity in your writing. So what is parallel structure and how does it work?

What is parallel structure?

Parallel structure means keeping your ideas in the same form throughout your sentence. For example, in the sentence, “Linda likes skiing, hiking, and spelunking,” each verb takes the gerund (-ing) form. In the non-parallel sentence, “Linda likes to ski, hiking, and to have spelunked,” each verb takes a different form. Not only is the second sentence grammatically incorrect, but it sounds awkward and is difficult to understand. 

Parallel structure also improves readability by removing ambiguity. Consider the phrase “comparing apples to oranges.” While the idiom infers that these two plural nouns are difficult to compare, the structure of the sentences allows us to understand that meaning with ease. If the phrase were “comparing apples to drinking orange juice,” the sentence becomes ambiguous. How do we even consider comparing the plural noun apples to the activity of drinking orange juice? Breaking parallel structure can render your sentences both incomprehensible and overly ambiguous.  

How do you check for parallel structure?

One trick to checking for parallel structure is to break apart and compare your coordinate elements to ensure they’re in the same form. For example, in the sentence “Tom preferred the desert for its dry days, cold nights, and small owls” break apart the italicized items and see if they’re in the same form:

Tom preferred the desert for its

                                                     dry days,

                                                     cold nights, and 

                                                     small owls.

In this sentence, each item follows the same pattern. See how this breaks in a different version of the sentence, “Tom preferred the desert for its dry days, because the nights are colder, and because he likes smaller owls rather than larger owls”:

Tom preferred the desert for its 

                                                     dry days, 

                                                     because the nights are colder, and 

                                                     because he likes smaller owls rather than larger owls.

In this sentence, each item follows a different pattern, breaking parallel structure. 

What else is there to know about parallel structure?

The purpose of this brief overview is to promote the use of parallel structure in your writing while highlighting a few examples. For more expansive overviews, consider grammar books like The Elements of Style, The Scribner Handbook for Writers, The Golden Book on Writing, or online resources like the Purdue University Online Writing Lab.