A gender identity is one's private sense of one's gender. There are many variations on gender, not just woman and man as described by the gender binary, these include (among others) genderqueer, and third gender.

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 the gender that is assigned to their biological sex. Some societies have so-called 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. Other cultures employ processes of surgical or hormonal sex reassignment to bring people's biological characteristics in line with their gender identity. In other societies, membership of either of the gender categories is open to people regardless of biological sex. It is an open question why the gender identities of some people conform or do not conform to the majority pattern, while others may not identify with any of the given gender categories. Whether these differences are a product of nature or nurture has been a contentious topic in the social and biological sciences. It is still an open question to what extent genetic versus social factors play a role in determining the gender identities of individuals.