The gender binary (also known as gender binarism) is the classification of gender into two distinct forms of masculine and feminine, whether by social system, cultural belief, or both simultaneously. Most cultures use a gender binary, having two genders (boys/men and girls/women).
In this binary model, gender and sexuality may be assumed by default to align with one's genetic or gamete-based sex, i.e. one's sex assigned at birth. This may include certain expectations of how one dresses themselves, one's behavior, sexual orientation, names or pronouns, which restroom one uses, and other qualities. For example, when a male is born, gender binarism may assume that the male will be masculine in appearance, have masculine character traits and behaviors, as well as having a heterosexual attraction to females. These expectations may reinforce negative attitudes, biases, and discrimination towards people who display expressions of gender variance or nonconformity or those whose gender identity is incongruent with their birth sex. Discrimination against transgender gender nonconforming people can take various forms, from physical or sexual assault, homicide, limited access to public spaces, in healthcare and more. The gender binary has been critiqued as a structure that maintains patriarchal and white supremacist norms.
The term gender binary describes the system in which a society allocates its members into one of two sets of gender roles and gender identities, which assign attributes based on their biological sex (chromosomal and genitalia). In the case of intersex people, the gender binary system is limited. Those who are Intersex have rare genetic differences which can give them the sex organs of both sexes or otherwise non-normative genitalia and may have difficulties fitting into the gender binary system.
Scholars who study the gender binary from an intersectional feminist and critical race theory perspective argue that during the process of European colonization in North and South America, a binary system of gender was enforced as a means of maintaining patriarchal norms and upholding European nationalism.