In morphology, a bound morpheme is a morpheme that only appears as part of a larger word; a free or unbound morpheme is one that can stand alone[1].
Affixes are always bound. English language affixes are either prefixes or suffixes. E.g., -ment in "shipment" and pre- in "prefix". Affixes normally carry only grammatical meaning.
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.
The morpheme ten- in "tenant" may seem free, since there is an English word "ten". However, its lexical meaning is derived from the Latin word tenere, "to hold", and this or related meaning is not among the meanings of the English word "ten", hence ten- is a bound morpheme in the word "tenant".
There are some distinguishable types of bound morphemes.
A cranberry morpheme[2][3] or unique morpheme[4] is one with extremely limited distribution so that it occurs in only one word. A popular example is cran- in cranberry" (hence the term "cranberry morpheme").
Unique morphemes are examples of the linguistic notion of fossilization: loss of productivity or usage of grammar units: words, phrases, parts of words. Besides fossilized root morphemes, there are also fossilized affixes (suffixes and prefixes).