Slang should be distinguished from jargon, which is the technical vocabulary of a particular profession. Jargon, like many examples of slang, may on occasion be used to exclude non-group members from the conversation, but in general has the function of allowing its users to talk precisely about technical issues in a given field.
Even within a single language community, slang tends to vary widely across social, ethnic, economic, and geographic strata. Slang may fall into disuse over time; sometimes, however, it grows more and more common until it becomes the dominant way of saying something, at which time it usually comes to be regarded as mainstream, acceptable language, although in the case of taboo words there may be no expression that is considered mainstream or acceptable. Numerous slang terms pass into informal mainstream speech, and sometimes into formal speech, though this may involve a change in meaning or usage.
