Gender arity, or leptarity, is a leptive method of describing gender systems. It categorizes gender system based on the number of established/existing gender categories within one's experience or within a given culture. The most well known gender arity is the Western gender binary. It is a gender arity of two, denoted by the prefix bi-, meaning that their are two established gender categories, in this case man and woman. However, this is not the only gender arity to exist. There are also cultures with five genders (quinary) or six genders (senary/hexary).
- Nullary: system in which no gender categories exists, or a conceptualization of gender that is not linked to any arity at all.
- Unary/monary: system in which one gender category exists.
- Binary: system in which two gender categories exist. It is most commonly understood to be male and female, and is present in Western cultures. The term abinary derives from this, showing a gender that is unrelated to the gender binary.
- Trinary/Ternary: system in which three gender categories exist. It is most commonly understood to be male, female, and a third gender, neutral gender, or androgynous gender. The term atrinary derives from this, showing a gender that is unrelated to the gender trinary.
- Quadnary/Quadrinary/Quaternary: system in which four gender categories exist.
- Quinary/Quinternary: system in which five gender categories exist. It is present in traditional Bugis culture.
- Senary/Hexanary: system in which six gender categories exist. It is present in traditional Jewish texts.