However, depending on what you're looking for, you can think about it in a few different ways:
* The opposite of the function of an adverb: Adverbs modify verbs, adjectives, and other adverbs. The opposite function would be a word that is modified by an adverb, like a verb, adjective, or another adverb.
* The opposite of the type of word: Adverbs are a part of speech. The opposite of a word type isn't really a thing, but you could think of other parts of speech like nouns, pronouns, verbs, adjectives, prepositions, conjunctions, interjections.
* The opposite of the meaning of an adverb: This depends on the specific adverb you are considering. For example, the opposite of "quickly" would be "slowly," and the opposite of "happily" would be "sadly."
Ultimately, "opposite" is a complex concept when applied to grammatical categories like adverbs. It's important to consider the specific context and what you're trying to express.