A morpheme is the smallest linguistic part of a word that can have a meaning , such as `` un - '' , `` break '' , and '' - able '' in the word `` unbreakable '' . The word `` unbreakable '' has three morphemes : `` un - '' , a bound morpheme ; `` break '' , a free morpheme ; and '' - able '' , a bound morpheme . `` un - '' is also a prefix , '' - able '' is a suffix .