副词（英文：Adverb）是一类用以修饰动词（相当于英文的动词）或加强描绘词组或整个句子的词，修饰名词的词一般为形容词，又称限制词。

一般而言，中文在一个词（通常是定语）的后面加「的」接主语或宾语，使定语成形容词，加「地」使其成副词，加「得」接状语表述结果，这是既有的明确语法守则，只是由于「的」、「得」、「地」在普通话里同音，一般人难以细察，因此，现在一般已经不太常做这种区别了。然而，由于这三个词在某些汉语族语言里（比如粤语）有不同的发音，因此，粤人大都能单凭平日的语用习惯，就能精确分辨这三个词的用法。

An adverb is a word that modifies a verb, adjective, another adverb, determiner, noun phrase, clause, or sentence. Adverbs typically express manner, place, time, frequency, degree, level of certainty, etc., answering questions such as how?, in what way?, when?, where?, and to what extent?. This function is called the adverbial function, and may be realised by single words (adverbs) or by multi-word expressions (adverbial phrases and adverbial clauses).