The English words bad and badly are often confused by English speakers. If you’re one of them, don’t feel bad, you won’t do as badly after reading this lesson.
Bad is an adjective, which means that it modifies nouns.
This is a bad movie.
That’s a bad idea.
Your English isn’t so bad after all.
Bad can be used with copular verbs (that is, verbs which express a state of being, such as to be, to seem, and to feel), but it is still an adjective modifying a noun, not a verb.
This movie is bad.
His ideas seem bad.
Don’t feel bad about your English.
Badly is an adverb, which means that it modifies verbs, adjectives, and other adverbs.
That movie did badly at the box office.
It was a badly-timed idea.
You don’t speak English badly.
Unlike its antonym "well," badly should not be use as an adjective to mean "in a bad way" or "sorry."
Yuck, this smells really
I feel so
badlybad for them.*
The Bottom Line
I think the confusion between bad and badly comes from their antonyms good and well. In most cases, good/bad and well/badly are used in the same situations, but the big exception is with the final examples. When you feel sorry for someone, you feel bad. "To feel badly" and "to smell badly" mean that you’re not good at feeling or smelling, just as "to play tennis badly" means that you’re not very good at tennis. You should only use badly for this latter meaning; for anything else, the only good choice is bad.