ABSTRACT
Allomorphic variation covers a wide range of issues and can be addressed from various perspectives. Although a general overview of the question is presented here, this chapter is basically centered on an analysis of allomorphy in Spanish within the Optimality Theory framework with a focus on a special case involving morphophonology, namely the diphthongization of the Vulgar Latin open mid vowels in tonic position and its overapplication in specific derived contexts such as evaluative derivation. I will also address an issue that has aroused considerable debate, which is the suitability of Optimality Theory for dealing with phonological opacity phenomena. There have been different attempts to solve this problem, from either parallel or stratal perspectives. Among the latter, this chapter will focus on the Stratal Optimality Theory model to address the aforementioned case of allomorphic variation in Spanish. By contrast, Transderivational Correspondence Theory evaluates output-to-output identity relations without intermediate levels and so displays the suitability of nonserial versions of Optimality Theory for handling opacity effects. Finally, one of the most important issues dealt with in this article is the difference between external (or optimizing) and internal (or nonoptimizing) allomorphy. While allomorph selection is subject to the Emergence of the Unmarked (TETU) effects in the external allomorphy—that is, allomorph choice improves unmarked structures—in the case of internal allomorphy the selection is arbitrary and must be lexically specified.
