Abstract
<jats:p>This chapter describes the competing grammars/grammar competition paradigm for analyzing synchronic variation, diachronic change and the variation found during changes in progress, and its role as the foundation for Yang's variational learning model of child language acquisition. The chapter first sets out the essential components of the paradigm, and then discusses some common objections (with particular attention to syntactic theory), indicating how these can be resolved. Then, ramifications of the paradigm are discussed in more detail, including its relation to issues within linguistics (Yang's variational learning model of acquisition, the variable rules of Labovian sociolinguistics, and Kroch's Constant Rate Effect) and extending beyond (to evolutionary dynamics as a way of understanding language change). The chapter includes brief discussions of the mathematical underpinnings of the model, but is intended to be comprehensible also to a reader who wants a non‐technical overview. We conclude that some notion of grammar competition is necessary for any coherent theory of language variation and change, and that grammar competition makes possible several important theoretical unifications in the above domains of linguistic theory.</jats:p>