Contextual conditions on stem alternations Illustrations from the Spanish conjugation*

This paper looks at the analysis of stem alternations: a type of non-affixal morphological change. Alternations of this type are controversial because they look in principle like they can be analyzed either with distinct stem forms in memory, or with (morpho)phonological rules that derive alternants from a single underlying form. I argue that the locality conditions on contextual allomorphy provide an answer to part of this controversy. It is shown that certain stem alternations in Spanish verbs–diphthongization, as in e.g. pensar/pienso (‘think’); raising, as in e.g. pedir/pido (‘ask’) – cannot be treated with stored stems, because the alternations do not occur under the locality conditions that apply to contextual allomorphy. These alternations must be treated (morpho) phonologically. The implications of this view are explored; this includes a conjecture that reclassifies different types of “morpheme specific” alternations in the grammar.