O'Grady et al. define dialect: "A regional or social variety of a language characterized by its own phonological, syntactic, and lexical properties." A variety spoken in a particular region is called a regional dialect; some regional varieties are called topolects, especially to discuss varieties of Chinese. In addition, there are dialect varieties associated with particular ethnic groups (sometimes called ethnolects), socioeconomic classes (sometimes called sociolects), or other social or cultural groups.
Dialectology is the study of dialects and their geographic or social distribution. Traditionally, dialectologists study the variety of language used within a particular , a group of people who share a set of norms or conventions for language use. More recently, sociolinguists have adopted the concept of the , a group of people who develop shared knowledge and shared norms of interaction, as the social group within which dialects develop and change. Sociolinguists Penelope Eckert and Sally McConnell-Ginet explain: "Some communities of practice may develop more distinctive ways of speaking than others. Thus, it is within communities of practice that linguistic influence may spread within and among speech communities."
The words dialect and accent are sometimes used interchangeably in everyday English speech, but linguists and scholars define the two terms differently. Accent is used to refer only to differences in pronunciation, especially those that are associated with geographic or social differences. Dialect, which refers to differences in syntax, morphology, and vocabulary as well as pronunciation, is the broader term.