Adverbs end in -ly and modify verbs. At least, that's what we're taught in elementary school.
It's a fair start, but we soon learn that adverbs are more complicated than the rule implies. For a start, adverbs can also modify adjectives, other adverbs, phrases, and clauses. And they don't have to end in -ly, either. Witness quite, however, and very.
Even knowing that, we sometimes regress to the first rule we learned, the elementary schoolteacher we've installed in our heads reminding us of our grammar basics and causing us to overcorrect ourselves.
One particular group of adverbs that causes our inner schoolteacher to rise up are flat adverbs. You might also here them called bare or immediate adverbs. These adverbs have the same spelling as the adjective form of the word: bright, easy, and fast, for example.
English used to have a long list of flat adverbs, but that list has dwindled in the last few centuries. Eighteenth-century grammarians (you knew they'd be involved, didn't you?) didn't understand how adjectives like cheap and late could be used as adverbs because (wait for it) that's not how Latin worked. These scholars concluded—incorrectly, it turns out—that instead of "Go slow," you should say "Go slowly."
Since then, language users have reduced the list, rejecting first one word and then another as not useful or ungrammatical. Here are some of the most common ones:
Flat adverbs fall into one of three categories:
- Those that don't have an -ly form.
- Those that have an -ly form with which they share meanings.
- Those that have an -ly form with which they don't share all meanings.
The first category is simple enough. Adverbs like fast just don't have -ly forms, so they move from adjective to adverb duty without much fuss:
Although Aunt Mary has a fast car, she doesn't like to drive fast.
In the second category, you'll find words like bright and quick. The bare and -ly forms are often interchangeable:
The sun shone bright that morning, causing the snow to melt quick.
The sun shone brightly that morning, causing the snow to melt quickly.
The third category is the most troublesome, because we don't always realize that while terms like hard and near have -ly forms, they aren't perfectly compatible. The two forms may share some senses of meaning but not all:
Tom worked hard at perfecting his golf swing.
Tom hardly worked at perfecting his golf swing.
There is a pattern, however, in this third category. Adverbs like hard, near, tight, and wrong generally can only follow their verbs and can often not modify anything other than a verb. Some of them have been fossilized in idioms, as well, such as sit tight.
Meanwhile, those adverbs' -ly forms have broader usage. They can go before or after the thing they modify and can modify more than a verb. They also have more definitions, so you're likely to see them more often.
The biggest problem with flat adverbs is that they are still losing status. As the list shrinks, we hear them less often. They often sound odd to our ears, unless they part of a well-worn phrase. Flat adverbs don't appear frequently in print and are often tolerated only in casual usage.
Though some usage experts label these words as mistakes or nonstandard, they are not. Yet that doesn't change their reception. You may wish to choose the more socially acceptable -ly form when it's available or a neutral synonym.
When in doubt about a flat adverb's meaning or usage, though, the solution is simple: check a dictionary. Your inner schoolteacher will be proud of you.