Found:

Root

MORPHOLOGY: a term which is not uniquely defined. Some linguists consider the root to be the basic free morpheme in a derived form. EXAMPLE: if we take the form disagreement, this word contains the basic free morpheme agree and the two bound morphemes (or affixes) dis- and -ment. Some linguists (e.g. Spencer (1991)) call agree the root. Others (e.g. Halle (1973)) assume that agree is the stem, and reserve the notion 'root' for bounded morphemes which cannot be considered as affixes. For example, if we take the words receive, conceive and deceive, we can isolate the prefixes re-, con- and de- and the bound morpheme ceive. Only Halle (1973) calls ceive the root.

LIT.	Halle, M. (1973) Spencer, A. (1991)