Speech communities are formed by language and social behaviors. Linguistics defines a speech community through many ways. All speech communities have a set of grammatical rules, phonology, syntax, and lexicons. As well as having social norms in which they share through actions. By a person's speech it can give an idea of a person's background in ways of where they are from, how educated one is, as well is if they are friendly or unsociable.
Now linguistic acculturation explains the process when two or more cultures collide for a long time they begin assimilate each other's language. In the most extreme cases of language shifts, pidgins and creoles are developed. Besides linguistic acculturation, the situation of bilinguals, some abandon their native tongue for another. Other bilinguals have a language used within the home different from outside of the home. This mostly refers to dialectal behavior. The second concept is superposed. This occurs when there are different activities going on in the same group.
Now Gumperz defines a speech community as "any human aggregate characterized by regular and frequent interaction by means of a shared body of verbal signs and set of from similar aggregates by significant differences in language use" (219). Gumperz feels as if people should share the same norm, communicate regularly, and share verbal signs.
Besides Gumperz definition there are three other definitions to a speech