In grammar, adverbial means doing the job of an adverb. An adverbial can be one word (quickly) or a longer group (in the morning, with a smile, because she was tired). So adverbial is wider than adverb: an adverb is a kind of word; an adverbial is a job in the sentence. A whole phrase can be adverbial even when no single word in it is an adverb. Teachers also use adverbial as a noun: this is an adverbial of time. It is classroom language, not everyday talk. You will meet adverbial phrase and adverbial clause in school books. Though actually, grammarians argue about the edges — is yesterday an adverb or a noun doing adverbial work? For learners, it is enough to ask: is this bit telling us how, when, where, or why?

副詞的、副詞性的。作名詞時，台灣中學多說副詞片語／副詞子句；對岸語法較常寫「狀語」。