An adverb is a part of speech that normally defines or describes a verb. It can also modify, or define, adjectives or sentences. A test for deciding if a word is an adverb would be to see if it answers the question ‘how’, ‘when’, or ‘where’. In the sentence, ‘Sally ran quickly.’ Sally is the noun/subject. Ran is the verb telling the action Sally took. The word quickly tells how Sally ran, so since it answers the question ‘how’ it is an adverb modifying the verb ran.