The document discusses language contact and bilingualism. It defines language contact as occurring when two languages are used in the same region and there is communication between speakers. This can result in language loss, bilingualism, or language change. Bilingualism is defined as an individual or society using two languages. Individual bilingualism depends on factors like language proficiency, acquisition context, age of acquisition, language domains, and social orientation. Code switching occurs when speakers alternate between two grammatical systems within a conversation and can be used for various social and communicative purposes.