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. Most cultures use a gender binary, having two genders (boys/men and girls/women); 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.
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 although Madison Bentley had already in 1945 defined gender as the “socialized obverse of sex”, 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.
Before Money’s work, it was uncommon to use the word 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 concept of a distinction between biological sex and the social construct of gender. Most contemporary social scientists, behavioral scientists and biologists, many legal systems and government bodies, and intergovernmental agencies such as the WHO, make a distinction between gender and sex.