Morpheme-based morphology

Morpheme-based morphology is a theory in which it is assumed that word formation rules may operate over morphemes (e.g. Halle (1973), Siegel (1974), Kiparsky (1982)). This theory is an alternative to the theory of word-based morphology (e.g. Aronoff (1976), Booij (1977), Scalise (1984)). In the latter theory it is assumed that new words are formed by applying a word formation rule to a single already existing word. Both the new word and the existing one are members of major lexical categories.

Example
English has the following verb classes:

(i)	X=fer	 X=mit	 X=sume   X=ceive    X=duce refer	 remit	 resume   receive   reduce defer	 demit		  deceive   deduce confer	 commit	 consume  conceive  conduce transfer transmit		    transduce

Apparently, we can isolate the prefixes re-, de-, con-, and trans- in these forms. However, the base forms fer, mit, sume, ceive, and duce do not exist as independent words. In a word-based morphology the words in (i) cannot be formed by a regular word formation rule. In a morpheme-based morphology, on the other hand, it is allowed to generate these verbs by prefixation rules. The question whether morphology is word based or morpheme based is still alive, and yet undecided.

Links
Utrecht Lexicon of Linguistics