Gender identity is a person's private sense, and subjective experience, of their own gender. This is generally described as one's private sense of being a man or a woman, consisting primarily of the acceptance of membership into a category of people: male or female. All societies have a set of gender categories that can serve as the basis of the formation of a social identity in relation to other members of society. In most societies, there is a basic division between gender attributes assigned to males and females. In all societies, however, some individuals do not identify with some (or all) of the aspects of gender that are assigned to their biological sex.
In most Western societies, there exists a gender binary, a social dichotomy that enforces conformance to the ideals of masculinity and femininity in all aspects of gender and sex - gender identity, gender expression and biological sex. Some societies have third gender categories that can be used as a basis for a gender identity by people who are uncomfortable with the gender that is usually associated with their sex; in other societies, membership of any of the gender categories is open to people regardless of their sex. (Full article...)