The document discusses the term "diglossia" which refers to a situation where two dialects or languages are used by the same language community. Diglossia was first introduced in English by linguist Charles A. Ferguson in 1959 to describe communities that use a primary, everyday vernacular variety as well as a separate, highly codified "high" variety for specific settings like literature, education, or formal situations. In linguistics, diglossia describes a single language community that uses two distinct forms of speech for different purposes.