A gender role is a set of social and behavioral norms that are generally considered appropriate for either a man or a woman in a social or interpersonal relationship. Gender roles vary widely between cultures and even in the same cultural tradition have differed over time and context. There are differences of opinion as to which observed differences in behavior and personality between genders are entirely due to innate personality of the person and which are due to cultural or social factors, and are therefore the product of socialization, or to what extent gender differences are due to biological and physiological differences.

Views on gender-based differentiation in the workplace and in interpersonal relationships have often undergone profound changes as a result of feminist and/or economic influences, but there are still considerable differences in gender roles in almost all societies. It is also true that in times of necessity, such as during a war or other emergency, women are permitted to perform functions which in "normal" times would be considered a male role, or vice versa.

Gender has several definitions. It usually refers to a set of characteristics that are considered to distinguish between male and female, reflect one's biological sex, or reflect one's gender identity. Gender identity is the gender(s), or lack thereof, a person self-identifies as; it is not necessarily based on biological sex, either real or perceived, and it is distinct from sexual orientation. It is one's internal, personal sense of being a man or a woman (or a boy or girl). There are two main genders: masculine (male), or feminine (female), although some cultures acknowledge more genders. Androgyny, for example, has been proposed as a third gender. Some societies have more than five genders, and some non-Western societies have three genders – man, woman and third gender. Gender expression refers to the external manifestation of one's gender identity, through "masculine," "feminine," or gender-variant or gender neutral behavior, clothing, hairstyles, or body characteristics.