bad, badly

Bad is the adjective, and badly is the adverb.

Use bad with linking verbs that express feeling, being, appearing or becoming:

• Do you still feel bad, or do you feel better now?
• Things are (or look) bad right now, but tomorrow is another day.
• Chicken will go bad if it is not refrigerated.

Use badly with action verbs and their forms (participles, gerunds, infinitives):

• The game went very badly for the home team after the second period.
• She sings so badly, her friends always ask her to stop.
• During the Depression, money was so badly needed, people sold their boots to buy food.
• Spelling badly can prevent you from communicating clearly.
• Matt knew he wouldn’t do well on his test, but he didn’t expect to do this badly.