Read the quotation below from Groucho Marx, one of the famous Marx brothers who made zany movies in the 1930s.

What if somebody was retelling this joke and said, “Other than a dog, a book is a man’s best friend. If you are inside a dog, it’s too dark to read.” It would no longer be funny, but why?

It’s because the revised statement lacks parallelism. Parallel structure involves the repetition of words, phrases, clauses, or sentences that have the same grammatical structure. “Outside of a dog” is a prepositional phrase, as is “inside of a dog.” These two parallel prepositional phrases make a listener want to think about the two structures similarly. However, “inside of a dog it’s too dark to read” makes the normal reading of “outside of a dog” (in other words, “other than a dog”) impossible. We expect the second phrase to be parallel to the first but have to revise our understanding when, although the structure is parallel, it doesn't go in the direction we expected. That's what makes this joke funny.

Nothing is less funny than having to explain a joke. However, the explanation makes one thing clear: Parallel forms have power.

If someone asked you why you like your three best friends, you might answer, “One has a great sense of humor, the second one has unlimited patience, and the third has a swimming pool.” Most people would mean this to be a joke, and most people would take it as a joke.

This joke doesn’t operate the same way that the Groucho Marx joke did. If you paraphrase it, though, you can see that the humor depends on parallel form. If you said, “One of my best friends has a great sense of humor; another one is very patient, and the third one lives in a house with a swimming pool in back,” the joke would lose its humor, and listeners might not think much of you.

In this case, the humor comes from a reader’s impulse to see all parts of a parallel construction as having the same importance, so the parallel construction implies that having a swimming pool is as important as a sense of humor and unlimited patience. If there is no parallelism, the statements about the friends are understood to have different degrees of importance.

* Parallel forms have power. They not only make things funny (sometimes), but they also make things clear, make things memorable, and even sometimes make things seem more reasonable than they otherwise would.

Plutarch, a Greek writer from the first century (46–120 AD), was not trying to be funny when he wrote the following:

Plutarch would not have made his point quite as well, though, if he had written, “I don’t need a friend who changes just because I change or a friend who sees me nod and decides that he should nod too.”

* The point of his statement is still there, but it has lost its style, its power, and its impact.

If parallelism isn’t clear to you, look back at the lesson in this course titled “Revision Strategies: Parallelism of Details.” This lesson will review parallel words (barks, jumps, and wags its tail), parallel phrases (by their beds, in their cars, or on the kitchen counter), parallel clauses (they should hire a driving school to teach their child to drive, and they should draw up a “driving contract” too), and parallel sentences (A good friend keeps you company. A great friend keeps you safe).

If, on the other hand, parallelism is clear to you, then you should have noticed two uses of parallel structure in the paragraphs above marked with asterisks. Check your understanding to see if you identified the parallels correctly.

In this lesson, you will practice using parallelism by recognizing parallels, seeing possibilities for parallels, and creating parallel constructions. Learn to use parallelism in your writing, and you will find it to be your most useful friend.