Abstract
This chapter surveys current theoretical approaches to the phenomenon of syncretism, that is, cases where morphology fails to mark a morphosyntactically relevant featural distinction. We first review arguments and evidence that the distinction between coincidental and systematic patterns of syncretism is linguistically relevant (‘psychologically real’). The chapter then turns to theoretical approaches to analyzing syncretism, including underspecification, impoverishment, rules of referral, and output-output faithfulness constraints. Next, the chapter discusses some typological trends, and consider the question of how cross-linguistic preferences for certain patterns over others might inform the theoretical analysis of syncretism. Finally, the chapter discusses the diachronic development of syncretism, focusing especially on the analysis of changes in the history of verbal inflection in Yiddish and Alemannic varieties of German.