An adverb is a word or an expression that generally modifies a verb, an adjective, another adverb, a determiner, a clause, a preposition, or a sentence. Adverbs typically express manner, place, time, frequency, degree, or level of certainty by answering questions such as how, in what way, when, where, to what extent. This is called the adverbial function and may be performed by an individual adverb, by an adverbial phrase, or by an adverbial clause.
Adverbs are traditionally regarded as one of the parts of speech. Modern linguists note that the term adverb has come to be used as a kind of "catch-all" category, used to classify words with various types of syntactic behavior, not necessarily having much in common except that they do not fit into any of the other available categories (noun, adjective, preposition, etc.).[1]