Bound and unbound morphemes

In morphology, a bound morpheme is a morpheme that appears only as part of a larger word; a free morpheme or unbound morpheme is one that can stand alone or can appear with other lexemes. A bound morpheme is also known as a bound form, and similarly a free morpheme is a free form.

Roots and affixes

Many roots are free morphemes, e.g., ship- in "shipment", while others are bound. Roots normally carry lexical meaning. Words like chairman that contain two free morphemes (chair and man) are referred to as compound words.

Affixes are always bound in English, although languages such as Arabic have forms which sometimes affix to words and sometimes can stand alone. English language affixes are almost exclusively prefixes or suffixes. E.g., pre- in "prefix" and -ment in "shipment". Affixes may be inflectional, indicating how a certain word relates to other words in a larger phrase, or derivational, changing either the part of speech or the actual meaning of a word.

Cranberry morphemes are a special form of bound morpheme that does not have an independent meaning or grammatical function, only serving to distinguish one word from another, as in cranberry, where the free morpheme berry is preceded by the bound morpheme cran-, which does not have independent meaning.