Linguistic term -- indivisible part of word that does not have a prefix or a suffix, may have a meaning and be usable alone or not
A word from which another word or words are derived.
The primary lexical unit of a word, which carries the most significant aspects of semantic content and cannot be reduced into smaller constituents. Inflectional stems often derive from roots.
The main part of an uninflected word to which affixes may be added to form inflections of the word. A stem often has a more fundamental root. Systematic conjugations and declensions derive from their stems.