Gender is a set of characteristics distinguishing between male and female, particularly in the cases of men and women. Depending on the context, the discriminating characteristics vary from sex to social role to gender identity. In 1955, sexologist John Money introduced the terminological distinction between biological sex and gender as a role; before his work, it was uncommon to use gender to refer to anything but grammatical categories. However, Money's meaning of the word did not become widespread until the 1970s, when feminist theory embraced the distinction between biological sex and the social construct of gender. Today, the distinction is strictly followed in some contexts, like feminist literature, and in documents written by organizations such as the World Health Organization (WHO), but in most contexts, even in social sciences, the meaning of gender has expanded to include sex or even to replace the latter word. Although this gradual change in the meaning of gender can be traced to the 1980s, a small acceleration of the process in the scientific literature was observed when the Food and Drug Administration started to use gender instead of sex in 1993. Gender is now commonly used even to refer to the physiology of nonhuman animals, without any implication of social gender roles.
In the English literature, the trichotomy between biological sex, psychological gender, and social sex role first appeared in a feminist paper on transsexualism in 1978.
Some cultures have specific gender-related social roles that can be considered distinct from male and female, such as the hijra of India and Pakistan.
While the social sciences sometimes approach gender as a social construct, and gender studies particularly do, the natural sciences, regard biological and behavioral differences in males and females as influencing the development of gender in humans; both inform debate about how far biological differences influence gender identity...