Deciding how and when to vary sentence length is not always easy. Is there a “just right” length for a particular sentence or idea? The answer depends on, among other things, the writer’s purpose, intended audience, and topic. A children’s story, for instance, may call for mostly short sentences, whereas an article on nuclear disarmament may call for considerably longer ones.

Although a series of short or long sentences can sometimes be effective, alternating sentence length is usually the best approach in formal writing. For example, after one or more long sentences with complex ideas or images, the punch of a short sentence can be dramatic:

The fire of, I think, five machine-guns was pouring upon us, and there was a series of heavy crashes caused by the Fascists flinging bombs over their own parapet in the most idiotic manner. It was intensely dark.

—GEORGE ORWELL, Homage to Catalonia

Similarly, try using a long sentence after several short ones.

Sith. What kind of a word is that? It sounds to me like the noise that emerges when you block one nostril and blow through the other, but to George Lucas it is a name that trumpets evil.

—ANTHONY LANE