词缀（affix）是一种附着在词根或词干的语素，为规范词素，不能单独成字。

根据词缀和词干结合位置的不同，可分为不同的词缀。前缀和后缀在语言中较常见，中缀和环缀较少见，因为他们在欧洲语言中并不常见。

An affix (in modern sense) is a morpheme that is attached to a word stem to form a new word. Affixes may be derivational, like English -ness and pre-, or inflectional, like English plural -s and past tense -ed. They are bound morphemes by definition; prefixes and suffixes may be separable affixes. Affixations, the linguistic process speakers use form different words by adding morphemes (affixes) at the beginning (prefixation), the middle (infixation) or the end (suffixation) of words.