Gener refers to the differences between men and women. Encyclopædia Britannica notes that gender identity is "an individual's self-conception as being male or female, as distinguished from actual biological sex." Although gender is commonly used interchangeably with sex, within the social sciences it often refers to specifically social differences, known as gender roles in the biological sciences. Historically, feminism has posited that many gender roles are socially constructed, and lack a clear biological explanation. People whose gender identity feels incongruent with their physical bodies may call themselves transgender or genderqueer.