For most, if not all, self-defined feminists, feminism means support for equality between women and men. The difficulty with this definition, though, is determining what one means by "equality," by "women and men," and by "sex" and "gender." For some feminists, equality requires that differences between women and men be acknowledged and valued. For other feminists, equality means that the category "human" encompasses women and men and that the differences within a sex are greater than differences between the sexes.

Feminists also differ on what they mean by "women" and "men"; these terms can be defined biologically, genetically, culturally, religiously, or psychologically. In academic feminism, convention has dictated that sex is defined by biology and that gender is defined by culture, but the debate continues as to how biology and gender influence each other and where one ends and the other begins. These debates about the nature of feminism have helped nurture an understanding of the complex interrelationship between biology and culture and have helped to broaden scholars' and activists' attention to different ways that oppression manifests itself.