Dialect v. Vernacular?

I am a little confused about the difference between dialect and vernacular. The definition I have for dialect is "The language of a particular district, cl, or group of persons. It encompes the sounds, spelling, grammar, and diction employed by a specific people as distinguished from other persons either geographically or socially. It is a major technique of characterization that reveals the social or geographic status of a character." Vernacular is "The everyday or common language of a geographic area or the native language of commoners in a country as opposed to a prestigious dead language maintained artificially in schools or in literary texts." My example is the language in To Kill a Mockingbird, and I'm trying to argue for it to fit into dialect. Help, anyone?