[header] How to use bad or badly and good or well [title] Determine whether your sentence needs " bad " or " badly ". [step] Locate the word that is being referred to by " bad " or " badly " (this word usually directly precedes bad/badly). If your sentence describes a person, place, thing, or idea, you will need to use an adjective. 
Adjectives are typically descriptive words that are used to further identify, or quantify nouns. " bad " is an adjective, so it should be used to identify or quantify nouns in your sentences.