Diglossia in Sociolinguistics
In sociolinguistics, diglossia is a situation in which two distinct varieties of a language are spoken within the same speech community. Bilingual diglossia is a type of diglossia in which one language variety is used for writing and another for speech. When people are bidialectal, they can use two dialects of the same language, based on their surroundings or different contexts where they use one or the other language variety. The term diglossia (from the Greek for "speaking two languages") was first used in English by linguist Charles Ferguson in 1959.
Diction Versus Diglossia
Diglossia is more involved than just switching between levels of diction in the same language, such as going from slang or texting shortcuts to writing up a formal paper for a class or report for a business. It's more than being able to use a language's vernacular. Diglossia, in a strict definition, is distinct in that the "high" version of a language isn't used for ordinary conversation and has no native speakers.
Examples include the differences between standard and Egyptian Arabic; Greek; and Haitian Creole.
"In the classic diglossic situation, two varieties of a language, such as standard French and Haitian creole French, exist alongside each other in a single society," explains author Robert Lane Greene. "Each variety has its own fixed functions—one a 'high,' prestigious variety, and one a 'low,' or colloquial, one. Using the wrong variety in the wrong situation would be socially inappropriate, almost on the level of delivering the BBC's nightly news in broad Scots." He continues the explanation:
"Children learn the low variety as a native language; in diglossic cultures, it is the language of home, the family, the streets and marketplaces, friendship, and solidarity. By contrast, the high variety is spoken by few or none as a first language. It must be taught in school. The high variety is used for public speaking, formal lectures and higher education, television broadcasts, sermons, liturgies, and writing. (Often the low variety has no written form.)" ("You Are What You Speak." Delacorte, 2011)
Author Ralph W. Fasold takes this last aspect a bit further, explaining that people are taught the high (H) level in school, studying its grammar and rules of usage, which they then apply to the low (L) level as well when speaking. However, he notes, "In many diglossic communities, if speakers are asked, they will tell you L has no grammar, and that L speech is the result of the failure to follow the rules of H grammar" ("Introduction to Sociolinguistics: The Sociolinguistics of Society," Basil Blackwell, 1984). The high language also has more intense grammar—more inflections, tenses, and/or forms than the low version.
Neither is diglossia always as benign as a community that just happens to have two languages, one for law and one for chatting personally. Autor Ronald Wardhaugh, in "An Introduction to Sociolinguistics," notes, "It is used to assert social position and to keep people in their place, particularly those at the lower end of the social hierarchy" (2006).Different Definition of Diglossia
Other definitions of diglossia don't require the social aspect to be present and just concentrate on the plurality, the different languages for different contexts. For example, Catalan (Barcelona) and Castillian (Spain as a whole) Spanish, don't have a social hierarchy to their usage but are regional. The versions of Spanish have enough overlap that they can be understood by speakers of each but are different languages. The same applies to Swiss German and standard German; they are regional.
In a bit wider definition of diglossia, it can also include social dialects, even if the languages are not completely separate, distinct languages. In the United States, speakers of dialects such as Ebonics (African American Vernacular English, AAVE), Chicano English (ChE), and Vietnamese English (VE) also function in a diglossic environment. Some people argue that Ebonics has its own grammar and appears related in lineage to Creole languages spoken by enslaved people of the Deep South (African languages melding with English), but others disagree, saying that it's not a separate language but just a dialect.
In this wider definition of diglossia, the two languages can also borrow words from each other.