What type of word is "quickly"?

"Quickly" is classified as an adverb because it describes how an action is performed. In English grammar, adverbs modify verbs, adjectives, or other adverbs, often providing information about the manner, frequency, degree, or timing of the action expressed by the verb. In this case, "quickly" tells us the speed at which an action is carried out, thus clearly functioning in the adverbial role.

For example, in the sentence "She runs quickly," "quickly" modifies the verb "runs," indicating the manner in which she runs. This distinct function of modifying actions is what confirms "quickly" as an adverb, distinguishing it from nouns, adjectives, or verbs, which have different roles in sentence structure.