This chapter covers the main sociolinguistic theories that have been applied to a common sub-type of language situation in the Creole-speaking Caribbean. The Creole-speaking Caribbean begins, at its most south-easterly extreme, on the shoulder of South America in French Guiana, extending westward to include Suriname and the Republic of Guyana. As part of a mathematical modelling of the Creole continuum in Guyana, Thomas and Devonish stumble on results that may help reconcile the seemingly contradictory perspectives of diglossia and Creole continuum. The chapter presents a more nuanced version of diglossia for Haiti and similar Caribbean situations. Diglossia is a modern sociolinguistic theory developed explicitly to explain language behaviour in a part of the Creole-speaking Caribbean. Communication within the Caribbean situations under study involves, at the macro-level, crude, diglossic-type language choices influenced by considerations of domain.