Affix

In linguistics, an affix is a morpheme that is attached to a word stem to form a new word or word form. The two main categories are derivational and inflectional affixes. Derivational affixes, such as un-, -ation, anti-, and pre-, introduce a semantic change to the word they are attached to. Inflectional affixes introduce a syntactic change, such as singular into plural (e.g. -(e)s), or present simple tense into present continuous or past tense by adding -ing or -ed to an English word. All of them are bound morphemes by definition; prefixes and suffixes may be separable affixes.