Abstract is: 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, in which gender is divided into two categories, and people are considered part of one or the other (boys/men and girls/women); those who are 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. In other contexts, the term gender is used to replace sex without representing a clear conceptual difference. For instance, in non-human animal research, gender is commonly used to refer to the biological sex of the animals. This change in the meaning of gender can be traced to the 1980s. In 1993, the US Food and Drug Administration (FDA) started to use gender instead of sex to avoid confusion with sexual intercourse. Later, in 2011, the FDA reversed its position and began using sex as the biological classification and gender as "a person's self-representation as male or female, or how that person is responded to by social institutions based on the individual's gender presentation." The social sciences have a branch devoted to gender studies. Other sciences, such as sexology and neuroscience, are also interested in the subject. The social sciences sometimes approach gender as a social construct, and gender studies particularly do, while research in the natural sciences investigates whether biological differences in females and males influence the development of gender in humans; both inform the debate about how far biological differences influence the formation of gender identity and gendered behavior. In some English literature, there is also a trichotomy between biological sex, psychological gender, and social gender role. This framework first appeared in a feminist paper on transsexualism in 1978.
Abstract is: Gender identity is the personal sense of one's own gender. Gender identity can correlate with a person's assigned sex or can differ from it. In most individuals, the various biological determinants of sex are congruent, and consistent with the individual's gender identity. Gender expression typically reflects a person's gender identity, but this is not always the case. While a person may express behaviors, attitudes, and appearances consistent with a particular gender role, such expression may not necessarily reflect their gender identity. The term gender identity was coined by psychiatry professor Robert J. Stoller in 1964 and popularized by psychologist John Money. In most societies, there is a basic division between gender attributes assigned to males and females, a gender binary to which most people adhere and which includes expectations of masculinity and femininity in all aspects of sex and gender: biological sex, gender identity, and gender expression. Some people do not identify with some, or all, of the aspects of gender assigned to their biological sex; some of those people are transgender, non-binary, or genderqueer. Some societies have third gender categories. The 2012 book Introduction to Behavioral Science in Medicine says that with exceptions, "Gender identity develops surprisingly rapidly in the early childhood years, and in the majority of instances appears to become at least partially irreversible by the age of 3 or 4". The Endocrine Society has stated "Considerable scientific evidence has emerged demonstrating a durable biological element underlying gender identity. Individuals may make choices due to other factors in their lives, but there do not seem to be external forces that genuinely cause individuals to change gender identity." Essentialists argue that gender identity is determined at birth by biological and genetic factors, while social constructivists argue that gender identity and the way it is expressed are socially constructed, instead determined by cultural and social influences. These positions are not mutually exclusive, as an innate gender identity can be expressed different ways in different cultures.