Warning: I've just realised I've been up all night and really need to get some sleep - so this is a post-and-run (until the evening). Second warning added: I tend to ramble a bit when tired. Apologies for the length!
Gender. Not the linked concepts of gender identity or grammatical gender, but the cultural expectations and impositions placed by societies on their members according to sex.
Like everyone else, I live in a society so am not free of externally applied or socially internalised gender. I have tried to resist it, personally and politically, since childhood. Since discovering feminism at 17, I've recognised it as a tool of patriarchal oppression.
I really hope people will run with it. Please raise questions, issues and share perspectives. We do this topic from time to time, so I'll kick off with a less-discussed angle: men 😄
A young male may grow up in a warlike society, which expects and requires men to be warriors. He may not feel himself to be warrior material, despite all his training. He may be distressed by violence, reluctant to hurt people, and far better suited to tending the wounded due to his irrepressibly kind disposition.
In a warrior society, violence defines a man. Our chap isn't violent, therefore he is not a man. He's kind and nurturing: qualities expected of a woman. By the logic of his culture, then, he is a woman - a woman with a penis (unless they cut it off to make sure). To make sense of him, they dress him in women's clothes and send him to do women's work, living with the women.
There is an obvious intersection here with gender identity and genderism. He might, if he were aware of the concept, 'identify as a woman' because this is the only explanation his society provides for a peace-loving male. We have evidence of this happening in Native American cultures with 'two-spirits' and archaeological finds of male skeletons with feminine trappings, among others.
It only means the guy 'is a woman' in terms of his people's highly prescriptive sex roles. The warrior stereotype for men still pertains in more flexible societies like ours: men are bigger, stronger than women, and more likely to be violent; in many ways the more physically dominant of men still overrule the gentler types.
It's one of the routes by which gender disadvantages males. There are others. By and large, though, sex stereotypes disadvantage women more widely and profoundly.