Speech community is a concept in sociolinguistics that describes a more or less discrete group of people who use language in a unique and mutually accepted way among themselves.

Speech communities can be members of a profession with a specialized jargon, distinct social groups like high school students or hip hop fans, or even tight-knit groups like families and friends. In addition, online and other mediated communities, such as Wikipedia, often constitute speech communities.

Speech communities, especially online, often develop terms that would be of little use to most people, but which is of value to the people involved. For instance, IRC develops such words as kick or op. Special terms that have emerged on Wikipedia include:

• Fancruft: a controversial term for articles about extremely minor details of an entertainment franchise or fictional universe. Characteristic examples of "fancruft" include articles about a single joke on The Simpsons or a Star Trek fanscript. Since many Wikipedia contributors consider the term derogatory, it has been bowdlerized into forms such as "f*ncr*ft" and "foghat."
• Requests for Comment or RfC: a process for gaining community input on controversies regarding article content and user conduct.
• Stub: a short article that needs expansion.

Members of a speech community will often develop neologisms such as those above to serve the group's special purposes and priorities. For example, the Wikipedia term stub arose from a need to identify and publicize articles that need to be expanded so they contain the detail and rich content that would be expected in a high-quality encyclopedia.

Stylistic features differ among speech communities based on factors such as the group's socioeconomic status, common interests and the level of formality expected within the group and by its larger society. In Western culture, for example, employees at a law office would likely use more formal language than a group of teenage skateboarders because most Westerners expect more formality and professionalism from practitioners of law than from an informal circle of adolescent friends. Speech communities will often change their use of language based on what situation they happen to be in at any given time. The speech of law practitioners is more formal in courtroom proceedings than in everyday office situations, while teenagers speak more formally when their parents are present than when they are not.

A person can (and almost always does) belong to more than one speech community. For example, a gay Jewish waiter would likely speak and be spoken to differently when interacting with gay peers, Jewish peers, or his co-workers. And if he found himself in a situation with a variety of in-group and/or out-group peers, he would likely modify his speech to appeal to speakers of all the speech communities represented at that moment.

(A variation on this concept is code-switching, which is usually observed among speakers of two or more languages who swtich between them based on the content or pragmatics of their conversation.)