In this dissertation, I propose a model of the Lexicon in order to have a satisfactory account of interactions between morphology and phonology. The model is a modification of Lexical Prosodic Phonology introduced in Inkelas (1989). The main point of this study is that there are three types of morphological operations defined by the number of prosodic domains constructed corresponding to one morphological domain. (1) Three types of morphological operations: (a) One that constructs two new prosodic domains; (b) One that constructs one new prosodic domain; and (c) One that does not construct any new prosodic domain. The first two types are cyclic, while the third one is noncyclic. The three types of morphology are referred to as compounding, cyclic affixation, and noncyclic affixation, respectively. Interaction between morphology and phonology in Japanese verbs provides arguments for the three-way distinction of morphology. Some rules apply only in compounding; some other rules take effect only in cyclic affixation; some rules take effect in all three morphological processes. Nonapplication of rules is due to either their structural description or their nonstructural property. In the former case, the structural description of a cyclic rule is not satisfied because of prosodic representation. In the latter case, a cyclic rule does not apply, even if the structural description is satisfied, because the domain is noncyclic.