This document discusses speech communities and language variation. It defines a speech community as a group that shares language practices and norms. Speech communities can be defined geographically, socioeconomically, ethnically/culturally, by age, or gender. The document also discusses that all languages exhibit variation in aspects like pronunciation, grammar and vocabulary. This variation can be regional, based on social factors like class, education, or the formality of the situation. Studies of language variation provide insights into how languages change over time.