Bound and free morphemes

In linguistics, a bound morpheme is a morpheme (the elementary unit of morphosyntax) that can appear only as part of a larger expression, while a free morpheme (or unbound morpheme) is one that can stand alone. A bound morpheme is a type of bound form, and a free morpheme is a type of free form. A form is a free form if it can occur in isolation as a complete utterance, e.g. Johnny is running, or Johnny, or running (this can occur as the answer to a question such as What is he doing?). A form that cannot occur in isolation is a bound form, e.g. -y, is, and -ing (in Johnny is running). Non-occurrence in isolation is given as the primary criterion for boundness in most linguistics textbooks. Affixes are bound by definition. English language affixes are almost exclusively prefixes or suffixes: pre- in "precaution" 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. Most roots in English are free morphemes (e.g. examin- in examination, which can occur in isolation: examine), but others are bound (e.g. bio- in biology). Words like chairman that contain two free morphemes (chair and man) are referred to as compound words. Cranberry morphemes are a special form of bound morpheme whose independent meaning has been displaced and serves only to distinguish one word from another, like in cranberry, in which the free morpheme berry is preceded by the bound morpheme cran-, meaning "crane" from the earlier name for the berry, "crane berry". An empty morpheme is a special type of bound morpheme with no inherent meaning. Empty morphemes change the phonetics of a word but offer no semantic value to the word as a whole. Examples: Words can be formed purely from bound morphemes, as in English permit, ultimately from Latin per "through" + mittō "I send", where per- and -mit are bound morphemes in English. However, they are often thought of as simply a single morpheme.