Rule composition makes it possible to model an important kind of deviation from the rule independence criterion – cases in which the application of one rule is directly dependent on that of another, carrier rule. In such cases, the only use of the dependent rule is as part of a composite rule incorporating both the dependent and its carrier. Where the definition of a word form involves two carrier rules, it can further happen that the same dependent rule composes with both of them, engendering a pattern of multiple exponence that deviates from the unique sequence criterion. I discuss two cases of this sort of rule dependency: Limbu verb morphology exhibits a pattern in which dependent rules compose with their carrier rules; Sanskrit presents a pattern of the reverse sort, in which a carrier rule composes with its dependent.

This chapter offers a first introduction to morphological theory by looking at several important theoretical debates. We begin by looking at the nature of morphological rules through the lens oftwo models: Item and Arrangement versus Item and Process models. We then consider the issue of lexical integrity, whether rules of syntax and rules of morphology can interact with each other. We consider the problem of blocking, competition, and affix rivalry. We also look at various ways of characterizing constraints on the ordering of affixes. We go on to look at the subject of bracketing paradoxes. The chapter concludes with a consideration of the nature of affixal polysemy.