Is It 'Feel Bad' or 'Feel Badly'?
We feel good about answering this question
"I feel so badly about correcting their grammar."
OR WAIT: "I feel so bad about correcting their grammar."
Which one is it? Feel is a verb, so shouldn't what comes after it be—and look like—an adverb?
The answer is: no.
Feel is a particular kind of verb called a linking verb. (Another term for linking verb is copula or copulative verb.) Linking verbs are not like regular action verbs. They function only to connect the subject of a sentence or clause with words that describe or identify that subject. And those words are either adjectives (or adjective phrases) or nouns (or noun phrases).
There are a number of linking verbs in English, among them be, become, seem, and all of the sensory verbs: smell, look, taste, sound, and feel. And while each of these can also be used as an action verb, it's easy to tell when they're being used as linking verbs, as in these cases involving the sensory linking verbs:
Those pies smell delicious. NOT: Those pies smell deliciously.
The pies look perfect. NOT: The pies look perfectly.
The crust doesn't taste too sweet. NOT: The crust doesn't taste too sweetly.
Their chewing sounds loud. NOT: Their chewing sounds loudly.
I feel bad that you didn't get any pie. NOT: I feel badly that you didn't get any pie.
Except let's stop at that last one again because, unlike the other "NOT" versions, we do, in fact, hear and read it—and often from people who know their way around an English sentence.
The common wisdom is that it's a case of "hypercorrection": we apply a rule of grammar in a situation that isn't quite the right one, and the result is a nonstandard linguistic form or construction. In this particular case, people who have learned to favor "it hurt badly" over "it hurt bad," and "need it badly" over "need it bad," use "feel badly" because they assume it is similarly superior to "feel bad."
If this is the case, though, why don't we also hear "I feel sadly" or "I feel angrily"? And why don't we also hear constructions like "smell awfully" and "look deliciously"?
As we said above, most linking verbs can also be used as regular old action verbs. Pies look delicious (where look is a linking verb), but we can also look at pies (where look is an action verb). Feel can also be an action verb, and when it's functioning as an action verb it's commonly followed by an adverb:
I feel strongly that the pies should be shared equally.
And that's where the goofy grammarian's joke about people who feel badly being unable to experience tactile sensations or being capable only of apathy comes from.
But some people make a considered distinction between feel bad and feel badly, choosing feel bad when feel is about physical health and feel badly when feel is about an emotional state. Others switch them with just as much intention. These uses are established enough that some dictionaries (including Merriam-Webster Unabridged) cover badly as an adjective; it is, after all, following a linking verb.
There was a time, mostly in the 19th century and mostly because bad was thought to only mean "somewhat evil," that people were advised to use feel badly for both physical health and emotional states. Modern advisers recommend feel bad in both contexts.
Interestingly, the same folks typically approve the use of feel well to describe one's health and feel good to sing along to James Brown. Feel good is also approved for both. Well and good are both adjectives in these cases. Which is, of course, all well and good.