He spoke quietly. They ran quickly. The last word in each of these two sentences is an adverb, a word that modifies a verb. We know that a complete sentence has a subject (a noun or a pronoun) and a verb, but adverbs are another part of speech that serves to add color and nuance to clauses. They’re a handy writer’s tool used to describe an action or give more detail about a verb. We’re usually able to spot adverbs easily, as most end in the letters “–ly.”
This is not always the case, though — a flat adverb is a descriptive word that’s missing that “-ly” suffix. Flat adverbs often look identical to their adjective counterparts, and both are used to modify or describe another part of speech. However, they differ in usage: Adverbs describe a verb instead of a noun. It seems simple enough, but many adverbs and adjectives are interchangeable.
Take, for example, the word “fast.” It can be used as both an adjective and an adverb. To use it as an adjective, you might say, “She was on the fast track to success.” In this example, the adjective “fast” describes the noun “track.” When “fast” is used as a flat adverb, though, the usage of the word changes. While still denoting quickness, in the phrase “she ran fast,” the flat adverb “fast” describes the speed of the verb “ran.”
There are, of course, regular adverb synonyms (“quickly,” “swiftly,” “hurriedly”) for the flat adverb “fast.” Each of these conveys a slightly different tone than the flat adverb, which helps explain why there are so many more regular adverbs than flat. If the goal is to add description, it’s usually worth using the most powerful word at your disposal.
