It’s a construct of a society. Different cultures will have different constructs, featuring different elements, and those things will change over time.
Those constructs are based on different elements, which again vary by culture. Some elements are seen as yes/no, on/off, present/not present. Others are perceived as more granular between extremes, where the extremes are frequently Masculine and Feminine. Yet others escape measurable evaluation. So, some elements are binary, some are on a spectrum, and some are agnostic without context, respectively.
Some elements associated with gender are based on genetic biological characteristics, but that’s legitimately a small fraction of them in most societies. The full list usually features hairstyles, clothes, facial decoration, vocal octave, vocal timbre, body part prominence, occupational skills, sexual skills, and even smells, among many other things.
You may notice that most of the examples I just gave are not binary. That was not always the case for many of them. The next thing to notice might be how hard it would be to define the extremes on a Masculine/Feminine spectrum for some of them. But of course, that likely depends somewhat on your cultural basis.
My thesis is that gender, as a construct, is pushing further and further away from genetic sex and genitalia. It always has been. I find that extremely interesting, but even more interesting is the potential for how gender, genetic sex, genitalia type, attraction, and sexuality will be able to interact in the future.
Imagine this: a genetic female with a vagina is attracted to and partnered with a genetic male with a penis, but due to their society’s current construct of gender and how these people appear within it, they consider themselves and are considered to be homosexual. Their genders are both perceived as predominantly masculine, which is their preference.
Or this: a genetic male with a penis is attracted to and partnered with a genetic male with a penis, and their society’s current construct and their own preferences on gender puts them both into a space outside of specific gender definition, so they have adopted a term which isn’t either the masculine or feminine extreme for their gender. Accordingly, they reject every defined term on the spectrum of sexuality which is based on the known gender extremes and have adopted one to include them. When they are ready to start a family, they will seek adoption.
You don’t have to imagine too hard, as both of those things are already happening today. A transsexual woman who has not gotten genital surgery can still find a home in the lesbian community, and nonbinary queer people can adopt children in most US states. But go back 20, 30, 50 years, and almost none of those things are true. And that doesn’t even get into monogamy and polyamory.
It’s also a lot of fucking words for things very fundamental to the human experience: Attraction. Love. Sex. Family. It takes some actual learning to grasp those words’ meaning and actual practice to use them properly.
That is ironically why we find ourselves here. As this gets more and more complicated, more and more people are inclined to give up. Some are nonchalant and adopt a policy of acceptance and tolerance. Others respond to their own ignorance with more ignorance, demanding others fit into the limiting labels and categories the ignorant think are set in stone.
Draw your own conclusions about which response will prove correct or more beneficial for its practitioners in the long term.
