A root is the portion of a word that
•is common to a set of derived or inflected forms, if any, when all affixes are removed •is not further analyzable into meaningful elements, being morphologically simple, and •carries the principle portion of meaning of the words in which it functions. Discussion
If a root does not occur by itself in a meaningful way in a language, it is referred to as a bound morpheme.
In linguistics, a stem is a part of a word. The term is used with slightly different meanings. In one usage, a stem is a form to which affixes can be attached.Thus, in this usage, the English word friendships contains the stem friend, to which the derivational suffix -ship is attached to form a new stem friendship, to which the inflectional suffix -s is attached. In a variant of this usage, the root of the word (in the example, friend) is not counted as a stem. In a slightly different usage, which is adopted in the remainder of this article, a word has a single stem, namely the part of the word that is common to all its inflected variants.Thus, in this usage, all derivational affixes are part of the stem. For example, the stem of friendships is friendship, to which the inflectional suffix -s is attached. Stems may be roots, e.g. run, or they may be morphologically complex, as in compound words (cf. the compound nouns meat ball or bottle opener) or words with derivational morphemes (cf. the derived verbs black-en or standard-ize). Thus, the stem of the complex English noun photographer is photo•graph•er, but not photo. For another example, the root of the English verb form destabilized is stabil-, a form of stable that does not occur alone; the stem is de•stabil•ize, which includes the derivational affixes de- and -ize, but not the inflectional past tense suffix -(e)d. That is, a stem is that part of a word that inflectional affixes attach to.