The chapter deals with sociolinguistics, the study of the influence of society and culture on language, including the way society and culture causes language change. This chapter looks at the preceding topics in this book (phonology, morphology, syntax, semantics, and pragmatics) with respect to their use by social groups. Regional variation, and the difference between language and variety, is explained. The impact of language contact on the development of language is discussed, along with the topics of pidgins and creoles. Variation among social groups is explored, along with the importance of awareness of linguistic bias.