The World Health Organization (WHO) defines gender roles as "socially constructed roles, behaviors, activities and attributes that a given society considers appropriate for men and women". Debate continues as to what extent gender and gender roles are socially constructed (i.e. non-biologically influenced), and to what extent "socially constructed" may be considered synonymous with "arbitrary" or "malleable". Therefore, a concise authoritative definition of gender roles or gender itself is elusive.
In the sociology of gender, the process whereby an individual learns and acquires a gender role in society is termed gender socialization.
Gender roles are culturally specific, and while most cultures distinguish only two (boy and girl or man and woman), others recognize more. Androgyny, for example, has been proposed as a third gender. Androgynous is simply a person with qualities pertaining to both the male and female gender. Other societies have claimed to identify more than five genders, and some non-Western societies have three genders – man, woman, and third gender. Some individuals (not necessarily being from such a culture) identify with no gender at all.
Many transgender people reject the idea that they are a separate third gender, and identify simply as men or women. However, biological differences between (some) trans women and cisgender women have historically been treated as relevant in certain contexts, especially those where biological traits may yield an unfair advantage such as sport.
Gender role, which refers to the cultural expectations as understood by gender classification, is not the same thing as gender identity, which refers to the internal sense of one's own gender, whether or not it aligns with categories offered by societal norms. The point at which these internalized gender identities become externalized into a set of expectations is the genesis of a gender role.