Morpheme

A morpheme is the smallest meaningful unit in a language. A morpheme is not identical to a word. Whereas words, by definition, always stand alone, a morpheme sometimes does not stand alone. For example, the word incoming is comprised of three morphemes: in, come and ing. Every word is made up of one or more morphemes. When a morpheme stands alone it is considered a root, and when it depends on another morpheme to convey an idea, it is called an affix (e.g. the -ing in coming).