A speech community is a group that decides how language will be used.
This community may be comprised of professionals familiar with language (linguistics, etymologies, etc.) that have a developed,
"professional jargon," but may also be made up of segments of society that influence the use of language in songs, slang, etc. Examples would include "high school students and "hip hop fans."
Microcosms of speech communities can even be as small as a close group of friends or even a family, where language evolves relative to those within that group. Words and phrases can be used in a nontraditional way, or words can be created.
The evolution of language can be seen with the advent of the Internet. We "surf" the web. The computer-user community has created new words like "blog."
In the television show NCIS, a part of the humor that the character Ziva David brings to the program is that she inaccurately uses the language, especially in terms of idioms. Her character's unintentional misuse of the language of the speech community she is now a part of (coming from another country and speech community), provides humor when she is corrected, and she processes the new information. For example, she might use the phrase "drip on his shoulder," when it should be "chip on his shoulder."
In terms of literature:
Exactly how to define speech community is debated in the literature. Definitions of speech community tend to involve varying degrees of emphasis on the following:
- Shared community membership
- Shared linguistic communication
This "discussion" regarding literature centers around the concept that "members" of speech communities adopt the same "linguistic norms." In other words:
...they share understanding, values and attitudes about language varieties present in their community.
The Webster-Merriam Online Dictionary defines speech communities, simply, as:
a group of people sharing characteristic patterns of vocabulary, grammar, and pronunciation
In literature, it can be assumed that any group of people within a novel or play, will speak in language patterns that are common to all, unless the piece is humorous and the breakdown of communication is part of the humor.
The "speech community" within a novel set in a Jewish community will use words common to that culture/religion. In the same way, a novel written about cowboys and gunslingers will use their own jargon, common to that "speech community."
If a story is written in the science fiction or fantasy genre, a new "jargon" may be created by the author for words that are specific to that book or series of books. Those who read the series regularly will be aware and understand the jargon used, but those reading for the first time may have to refer to the glossary of terms, often included in these kinds of books. In this way, a new speech community is created.