: female (left), male (right). From symbols for Venus and Mars.]]Gender, in common usage, 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."[LINK: http://www.britannica.com/eb/article-9036351] Gender Identity, Encyclopædia Britannica Online, 2007. 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 gender roles to be socially constructed, independent of any biological basis. People whose gender identity feels incongruent with their physical bodies may call themselves transgender or genderqueer. Many languages have a system of grammatical gender, a typ