That is just one definition of gender. There's confusion over its usage because it has a number of different and conflicting meanings. In her book Material Gir

That is just one definition of gender. There's confusion over its usage because it has a number of different and conflicting meanings. In her book Material Girls, which thoroughly and thoughtfully explores this topic, Kathleen Stock describes four senses of the word: > GENDER1: A polite-sounding word for the division between men and women, understood as a traditional alternative word for biological sex / the division between biological males and females. > GENDER2: A word for social stereotypes, expectations and norms of 'masculinity' and 'femininity', originally directed towards biological males and females respectively. These can and do differ from culture to culture, though there are many overlaps too. > GENDER3: A word for the division between men and women, understood, by definition, as a division between two sets of people: those who have the social role of masculinity projected onto them, and those who have the social role of femininity projected onto them. > GENDER4: A shortened version of the term 'gender identity'. [A] common idea is that it is the 'private experience of gender role' - roughly, whether you relate to yourself psychologically as a boy or man, girl or women, or neither, in a way that has nothing directly to do with your sex. Up until recently, the colloquial sense was GENDER1. Now this is shifting partly towards GENDER4, amongst some but certainly not all English speakers. When you refer to people "confounding sex and gender", I expect you're simply observing the conflict between different people understanding the term as GENDER1 or GENDER4.