The gender binary is a concept or social system that claims there are only two genders—female and male—that form a binary or pair. It generally assumes that it is "normal" for people to be cisgender,since gender identity is expected to always align with the sex that was assigned at birth. Men and women are also expected to conform with their culture's expectations regarding gender expression and gender roles. Variations in identity or expression are not understood, recognized, or supported. The gender binary thus reinforces strict gender roles by treating gender essentialist beliefs as factual. It does not reflect the reality of people's experiences and has been disproven.