Gender is the range of characteristics pertaining to femininity and masculinity and differentiating between them. Depending on the context, this may include sex-based social structures (i.e. gender roles) and gender identity.[1][2][3] Most cultures use a gender binary, having two genders (boys/men and girls/women);[4][5][6] those who exist outside these groups may fall under the umbrella term non-binary. Some societies have specific genders besides “man” and “woman”, such as the hijras of South Asia; these are often referred to as third genders (and fourth genders, etc.). Most scholars agree that gender is a central characteristic for social organization.[7]

Sexologist John Money is often regarded as the first to introduce a terminological distinction between biological sex and “gender role” (which, as originally defined, includes the concepts of both gender role and what would later become known as gender identity) in 1955[8][9] although Madison Bentley had already in 1945 defined gender as the “socialized obverse of sex”,[10][11] and Simone de Beauvoir‘s 1949 book The Second Sex has been interpreted as the beginning of the distinction between sex and gender in feminist theory.[12][13]

Before Money’s work, it was uncommon to use the word gender to refer to anything but grammatical categories.[1][2] However, Money’s meaning of the word did not become widespread until the 1970s, when feminist theory embraced the concept of a distinction between biological sex and the social construct of gender. Most contemporary social scientists,[14][15][16] behavioral scientists and biologists,[17] many legal systems and government bodies,[18] and intergovernmental agencies such as the WHO,[19] make a distinction between gender and sex.