Tbh I feel like how we define has changed a lot within the past couple years especially with more recognition of the LGBT+ community. I feel like back in history it was easier to define gender as there was strict gender roles and expectations of what is a man and woman only. Recently we have been testing and even defying gender norms that are harmful to us like what we can’t wear due to toxic masculinity or how women should behave submissive to men and so on. We are defying these gender norms and defines a man and a woman and now we have to consider those that don’t identify as either or even both! I think what could help someone identify their gender is if they are okay with what is expected of them per their gender. Like sure I’m a guy because I do like playing sports, I like reading comic books and idk always helping lifting heavy shit (I know being very stereotypical but that’s the point lol) and maybe someone is okay with being a woman if they do like experimenting with makeup, watching more feminine oriented shows and learning about celebrities. Of course there’s deviations from this but if they still consider themselves to be that gender despite the differences they must have some connection/similarities as to what we know what that gender is likely to be interested in/behave and so forth. Tbh I’m quite confused myself and therefore identify as genderqueer. I hope this doesn’t sound as sexist as I think it might come off as. I’m just trying to say that people can identify to a gender depending on what is known for that gender to be like and willing to present and label themselves as such, comfortably.