Like any dialect, a nonstandard dialect has its own vocabulary and an internally consistent grammar and syntax; and it may be spoken using one or a variety of accents. As American linguist John McWhorter describes about a number of dialects spoken in the American South in earlier U.S. history, including older African American Vernacular English, "the often nonstandard speech of Southern white planters, nonstandard British dialects of indentured servants, and West Indian patois, [they] were nonstandard but not substandard." In other words, describing a dialect as "nonstandard" is not intended to imply that the dialect is incorrect, incomplete, or inferior, just that it is not the socially perceived norm or mainstream for public speech. In fact, linguists consider all nonstandard dialects to be grammatically full-fledged varieties of a language. Conversely, even some prestige dialects may be regarded as nonstandard.
As a border-case, a nonstandard dialect may even have its own written form, although it's then to be assumed that the orthography is unstable and/or unsanctioned, and that it is not orderly supported by governmental or educational institutions. When used in quotes and as a contrastive feature in literature, the term eye dialect may be used for nonstandard phonemic spelling.
It is uncommon in written texts unless the text is dialect poetry, etc.
- McWhorter, John H. (2001). Word on the Street: Debunking the Myth of a "Pure" Standard English. Basic Books. p. 152.