Gender is the range of characteristics pertaining to, and differentiating between, femininity and masculinity. Depending on the context, these characteristics may include biological sex, sex-based social structures (i.e., gender roles), or gender identity. Most scholars agree that gender is a central characteristic for social organization. Most cultures use a gender binary, having two genders (boys/men and girls/women); those who exist outside these groups fall under the umbrella term non-binary or genderqueer. Some societies have specific genders besides "man" and "woman", such as the hijras of South Asia; these are often referred to as third genders (and fourth genders, etc.).