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|Spectra and binaries|
The gender binary is the commonly held view that individual humans belong to one particular gender category: either male or female. It enforces conformity to socially-acceptable forms of gender expression, such as choices in clothing, careers, and romantic and sexual partners. Most people do not think of the gender binary as an ideology, as it is so ingrained in the public consciousness; nevertheless. The idea that there are two genders and that every person must fit into one of them is historically contingent and a socially-constructed phenomenon.
In recent years, as gender has become more widely studied, the socially-constructed nature of the gender binary, and the uneven power relationships it produces and maintains, have become the subject of growing critique.
Many individuals do not fall under the firm constraints dictated by the gender binary. Intersex people are born with genitals not matching their DNA karyotype, or with a deformed or intermediate set. An XX fetus may have congenital adrenal hyperplasia, causing excessive androgens which results in male development, and an XY fetus may have androgen insensitivity syndrome, causing female development. Transgender people, broadly speaking, adopt traits of genders not matching their birth sex—people identifying as genderqueer, bigender, genderless, and so on may reject traditional categorization whatsoever. Transsexual people present a somewhat unique case, as their gender expression does not break the gender binary, but moves from one side to the other. There are also some countries such as Australia and India that recognize a third gender, either formally or informally.
The backlash against the gender binary has produced movements aiming to broaden the range of recognized gender categories, or abolish gender as a legal and/or social concept entirely.