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The gender binary, also referred to as gender binarism (sometimes shortened to just binarism), is the classification of sex and gender into two distinct, opposite and disconnected forms of masculine and feminine. It is one general type of a gender system. As one of the core principles of genderism, it can describe a social boundary that discourages people from crossing or mixing gender roles, or from identifying with three or more forms of gender expression altogether.
The term gender binary describes the system in which a society splits its members of male and female sexes into gender roles, gender identities and attributes. Gender role is one aspect of a gender binary. Many societies have used the gender binary to divide and organize people, though the ways this happens differs between societies. Gender binaries exist as a means of bringing order, though some, such as Riki Wilchins in GenderQueer: Voices from Beyond the Sexual Binary, argue that gender binaries divide and polarize society. Certain notable religions are often used as authorities for the justification and description. Islam, for example, teaches that mothers are the primary care givers to their children and Catholics only allow males to serve as their priests.
Exceptions have widely existed to the gender binary in the form of specific transgender identities. Besides the biological identification of intersex individuals, elements of the both or neither sexes have been taken by people biologically female and male such as Two-Spirited Native Americans and hijra of India. In the contemporary West, transgender people break the gender binary in the form of genderqueer. Transsexuals have a unique place in relation to the gender binary because in many cases their gender expression transitions from one side of the gender binary to the other but still conforms to the gender binary itself.
Many scholars have contested the existence of a clear gender binary. There is an increasing amount of research that illustrates that the evidence for dividing humans into the two distinct categories of men and women is problematic and a self-fulfilling prophecy. For example, Judith Lorber explains the problem of failing to question dividing people into these two groups “even though they often find more significant within-group differences than between-group differences.” Lorber argues that this corroborates the fact that the gender binary is quite arbitrary and leads to false expectations of both genders. Instead, there is growing support for the possibility of utilizing additional categories that compare people without “prior assumptions about who is like whom.” By allowing for a more fluid approach to gender, people will be better able to identify themselves however they choose, and scholarly research will find different similarities and differences. Gender activist Gopi Shankar, a student of The American College in Madurai, penned what he claims is the world's first book on Gender-Variants in Tamil.
A further issue with the gender binary is the insistence that men are masculine and women are feminine. This reduces options for people to act outside of their gender role without coming under scrutiny. Moreover, male and female do not directly translate to masculine and feminine as those terms are laden with ulterior meanings that have been “politically contextualized and constructed” and are not mutually exclusive categories. Therefore, the assertion of femininity applying solely to women and masculinity solely to men is fundamentally flawed. It is important to distinguish femininity and masculinity as a descriptor for behaviors or attitudes without tying them directly to the genders man and woman. By employing masculinity and femininity as adjectives, they are helpful tools for understanding human actions. Gendered descriptors have uses, but by connecting them to specific sexes they become oppressive terms that enable continued discrimination.
Maria Lugones observes that among the Yoruba people there was no concept of gender and no gender system at all before colonialism. She argues that historically a gender system was introduced by colonial powers as a tool for domination and fundamentally changing social relations among the indigenous.
The study of transgender individuals is seen as an indication of the lack of a binary. A person can exhibit both traits that were rendered exclusive to “girl” or “boy”. Anne Fausto-Sterling suggests a classification of five sexes and a move away from the socially constructed gender binary classification of “male” and “female.” In her paper “The Five Sexes: Why Male and Female Are Not Enough,” she exposes the existence of intersexuals, individuals possessing a combination of male and female “parts,” who are seen as deviations from the norm and who need to be “fixed” in order to maintain the two-gender system. The existence of these individuals challenges the standard gender binary and puts into question society’s role in constructing gender. Fausto-Sterling indicates that modern practitioners encourage the idea that gender is a cultural construct and concludes that, “we are moving from an era of sexual dimorphism to one of variety beyond the number 2.” 
- Butch and femme
- List of transgender-related topics
- Non-binary discrimination
- Sexual dimorphism
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- Fausto-Sterling, Anne (March–April 1993). The Five Sexes: Why Male and Female Are Not Enough. The Sciences. pp. 20–24.
- GenderQueer: Voices from Beyond the Sexual Binary (Alyson), (Joan Nestle, Clair Howell Co-Editors) 2002 ISBN 1-55583-730-1
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