考察俚语的概念。
Slang is a casual use of language that consists of expressive but nonstandard vocabulary, typically of arbitrary, flashy and often ephemeral coinages and figures of speech characterized by spontaneity and sometimes by raciness. Although slang is often very vivid and expressive and almost everyone uses it on some occasions, the term slang has traditionally carried a negative connotation: it is often perceived as a low or vulgar form of language and is deemed to be undesirable in formal styles of language.