This chapter situates plurilingualism (at the individual level) and multilingualism (at the societal level), depending on the researcher’s approach to language contact, as enablers of various consequences of language contact. The relevant phenomena include language endangerment and loss (through language shift), codemixing and codeswitching (or translanguaging), the emergence of creoles, other mixed language varieties (including urban youth “stylects”), colonial varieties of European languages (such as Spanish), super-diversity, as well as structural change, borrowing, and the emergence of lingua francas. Concepts such as foreign workers’ interlanguages are contrasted with creoles and pidgins. Differences in their emergence are grounded in second language learning, degree and type of exposure to the hegemonic language, language shift, and the emergence of communal norms. The presentation in the chapter is generally grounded in population movements and changing population structures, therefore in speakers'/signers’ social history. It is also diachronic, explaining how domains of interest have evolved and expanded in language contact as a research area since the late nineteenth century, focusing on phenomena not elaborated in the chapters of Volume 1.