Let's take this argument you present and apply it to an obvious case. If you say gender is associated with traits, then here s trait, having a penis. I know a trans woman who was born with a penis. Is having a penis a trait of gender? Does having a penis make her a man? If gender is associated with traits, biological traits you mentioned such as being tall, well having a penis counts as a biological trait. Just as you argued there exist women who are born tall, and that doesn't make them any less of a woman. We can't assume that everyone born must be a man. Perhaps we can do the same with a penis. It's just a biological trait, like being tall. Can we then argue that just as some women are born tall, as tall as 6 foot 7, some women may just be born with penises. Having a penis doesn't make them being a man any more than being tall makes them a woman. So some women are born with penises, that doesn't make them men. We could argue just as the physical trait of being tall doesn't make someone being a man, being born with a penis doesn't either. Here's another physical trait, chromosomes. So most women are born with XX chromosomes. Some women are not. Some women are born with other chromosome combinations, maybe even XY, XXY, XXXY, etc. So, perhaps, just as some women, very few women are tall, some women may be born with XY chromosomes, and penises Those are called trans women. There you go, your own argument supports this. Just because the majority of women born don't have penises, and have XX chromosomes, doesn't mean that mean determines gender. These are traits of gender, not the definition.