An ethnic group (or ethnicity) is a group of people whose members identify with each other, through a common heritage, often consisting of a common language, a common culture (often including a shared religion) and an ideology that stresses common ancestry or endogamy. Another definition is "...a highly biologically self-perpetuating group sharing an interest in a homeland connected with a specific geographical area, a common language and traditions, including food preferences, and a common religious faith".
Members of an ethnic group are conscious of belonging to an ethnic group; moreover ethnic identity is further marked by the recognition from others of a group's distinctiveness. Processes that result in the emergence of such identification are called ethnogenesis.
Source: Wikipedia, Link