Vernacular is defined in two important ways; it is a language or dialect spoken in a particular place or region. Also, in a literary sense, it is a choice that a writer makes in employing informal, everyday speech for characters that is often informed by dialect.

There are many examples of American writers who have used vernacular in constructing plays, novels, and short stories. Mark Twain's use of vernacular in The Adventures of Huckleberry Finn in the characterizations of Jim and Huck are particularly effective. When Huck, an uneducated white boy, and Jim, an African American escaped slave, first encounter each other on the island after Huck has faked his own death, the two have a conversation in the vernacular of 19th century Missouri:

“Strawberries and such truck,” I says. “Is that what you live on?”

“I couldn’ git nuffn else,” he says.

“Why, how long you been on the island, Jim?”

“I come heah de night arter you’s killed.”

“What, all that time?”

“Yes—indeedy.”

“And ain’t you had nothing but that kind of rubbage to eat?”

“No, sah—nuffn else.”

In Harper Lee's 1960 novel To Kill a Mockingbird, the setting is Alabama during the Depression era, sometime in the 1930s. Walter Cunningham speaks in vernacular when he tells Atticus Finch about the difficulty he has with school:

Reason I can’t pass the first grade, Mr. Finch, is I’ve had to stay out ever’ spring an’ help Papa with the choppin’, but there’s another’n at the house now that’s field size.

And finally, in Willa Cather's O, Pioneers!, the author seeks to capture the Swedish-American vernacular of the immigrants to Nebraska in the late nineteenth century. Alexandra's father calls to her:

“DOTTER,” he called feebly, “DOTTER!” He heard her quick step and saw her tall figure appear in the doorway, with the light of the lamp behind her.

Many works of American Regionalism are often noted to employ vernacular.