"Ora, in regards of humans (as opposed to words. I wouldn't say words have
sex. That would just be kinky) and the noun, not the act, yes. I actually don't
really see the need for the word gender in regards to humans. "
And up until fairly recently i probably would have agreed with you. As a femenist i believe in gender equality. And i would have said that a world where gender expression was not normalized or was banned would be better - but tyat was before i gained an understanding and empathy for transgender friends. Gender identity and expression being two seperate things - obviously a man can present himself as a woman, and actors have for years done so; and a woman can present as a man, and women posing as male soldiers have fought in many wars. But gender identity is needed, there is a part of the brain which categorises like and different, and trangirls (as young as the age of 4) will clearly identify themselves as like the other girls, and unlike the boys. They feel bad when they are told they can't take part in normal girly activities and will no understand why.
Even if they don't really like doing the activities.
I think there is sufficient evidence that this is different from a tomboy who likes to play with other boys (cause their activities are more fun) but still categorises herself as a girl. This is similar in a way to sexual orientation because you can't see sexual orientation, it's in your head, you can assume a person is gay/straight based on who they are fucking/holding hands with - but they could easily be bisexual, or asexual (and not attracted to their partner at all, but fucking them cause they want to or feel obliged to)
Similarily gender identity can only really be known to a person themselves, and we can listen to wha they say (they could choose not to present as the gender they identify with, just as a man in prison could choose to have anal sex with his bunk mate - that doesn't change their sexual orientation/gender identity)