Beginning with the connection between language and society and the history of social thought and linguistic theory, this chapter discusses the development of empirical work on variability in language use in social settings. It describes progress in sociolinguistics and how analysis of speech in relation to the social backgrounds of speakers in heterogeneous, stratified societies, e.g., their racial and ethnic affiliations, migration histories and power relations, relationships in multilingual settings, etc., rested on new methodologies and created new findings about linguistic diversity.

Guided by work on speech communities, sociolinguists found various patterns in the relation between language and society (including language change) by studying: ‘free variation’; language use in specific sociocultural settings (engendering ‘ethnography of communication’); language contact and pidgins/creoles; bi/multilingualism, language choice (engendering ‘sociology of language’) and code-switching; language use in diglossia (related to functional domains, social situation, interlocutor, subject matter, etc.).

Working with sociolinguistic variables, such as space, time, social class, ethnicity/race, sex/gender, and age, which constitute a complex object of multidimensional variability, the sociolinguist Labov found, e.g., that race/ethnicity and gender differences were more important than social class for language change in the USA.

Given these issues, the problem of identifying the linguistic system is complex and paramount.