Sex.Loosely defined, sex is what's in your genes/jeans. How did the sex cells recombine?
My basic 300 level college genetics course dealt in X and Y chromosomes. These mostly pair up, as chromosomes do. XX produces female offspring. XY produces male. They are usually differentiated by a check of the progeny's genitals. The chromosomes do combine in other ways: XXY, XYY, XXX, X0 being the most common.
Because of the chromosomes, puberty triggers hormones in humans to develop secondary sexual characteristics.
We are born male and female. We become men and women.
Gender is how we behave. As I had one character tell another, "Being a man is here " he tapped his forehead, "and here" he tapped his chest, "not what's between your legs." Sex is what's between your legs, gender is head and heart.
Most people's gender matches their bio-sex. They perform according to societal norms and never question. In a highly conformative environment, say white middle America, any deviation is seen as a threat to well, everything: sex, the family, religion and probably the country itself. There is some latitude for girls to perform some masculinity, tomboys, but very little for boys to perform any femininity.
Some people, their mental gender doesn't line up with their body. This is where transgender comes in. It's no longer called a sex change or transsexual, since the sex of the patient is not actually changed (although the hormonal therapy necessitates medical professionals treating the patient as not only the sex but the gender as well)
Masculinity and Femininity
These are how Man and Woman are performed. They are defined by dress, activity, societal expectation and sometimes law.
Many who are genderqueer and non-binary criticize transfolk for performing their gender so close to stereotypes. But in order to be taken seriously, the masculinity or femininity must be performed strongly to counter the other visible markers that say the person's body does not match their presentation.
There are many performances for masculinity and more for femininity. These can be played with to a degree. The problems crop up in other people's minds when they've gotten used to thinking of a person one way, and then that person performs outside of the accepted boundaries.
My junior husband is not a jock or a manly man. He's a rather fem man, and sometimes he's a boy in a dress. The dress disconcerts me because I associate it with my former girlfriend. I run rather more masculine in my positions. Because if I'm going to be a man, I'm going to be one where there is no question about my manliness. (I refused to be a sissy, even as a girl)
Nonbinary folks may be saying I'm thinking in stereotypes and that the dress shouldn't make a difference. Perhaps it shouldn't but it does. Part of me thinks "When I'm a man, I'll have to give up skirts in the summer, certain perfumes, cool socks and a lot of jewelry. Because otherwise, I might as well stay a woman."
I don't perform femininity often or well. I've called it "doing drag" for over a decade now. Being required to do so can feel restrictive, but losing the option to do so can feel just as bad.
Where I am
Right now, I'm starting to change over my online life. I have to stay a woman for a while, because the gods have crone work for me to do.
Right now, I'm stepping into a whole new world, one where I'm behind the times in many ways and not sure I can catch up. (I still call it Making The Change)
Right now, I'm hesitant to be around other transfolk, especially younger ones, because I know I'll screw up and get corrected. Sometimes it's a useful correction, sometimes it's a jumping on. And I've been on the net long enough to respond with endless sarcasm to the latter.
Right now, I'm sorting out the outcomes of changing over, and kind of horrified the best conclusion I'm finding for me is a eunuch in a suit, a bitch with a beard and boxers essentially. I don't have any interest in make-believe sex or toys. Surgery is chancy at best (55% reported complications, only 9% had erogenous sensation and only half were able to perform sexually) and moreso as I age.
I will never be male. I'm stuck with a XX body.
I might be able to be a man, heart and head after all, with some artificially-created secondary sexual characteristics.
I can perform masculinity. Half the reason most people think I'm a bitch is because I say things with authority and without qualifiers. I've been performing masculinity for years. It;'s more of the same.
I'd just like a mustache to twirl as I do.