To Be A Woman

What is a woman? My seminar class was on gender roles. And I suppose I have yet to completely figure this question out. I learned what are typical feminine and masculine characteristics, but I also learned the characteristics are this way because woman are supposed to be feminine and men are supposed to be masculine and how these characteristics are instilled beginning in childhood. They were many feminine men and masculine women. But what makes a woman? Reading The Second Sex, I'm still not too sure. Does it truly matter whether one is a woman or a man? I'm not sure I'll ever know what exactly a woman and a man is, forgoing sexual body parts.