As a child, I believed that Canadians had no culture; presumably, I saw "culture" as the ways in which people from different countries acted differently, and since we all acted "normally", we therefore had no culture.
Gender identity seems...complicated. Generalization based on abstraction is the basis of how humans think and communicate, so we like to put things in neat categories. Naturally we want to put ourselves, and even other people into neat categories, even when this is nonsensical, or harmful.
I try to think in terms of continua, rather than binary classifications. Cisexual/transexual isn't a thing; it's a range of things.
Please don't get triggered by my particular choice of nouns below; I don't think they match the standard lexicon, but they're what I've got to work with. This general model has been lurking in my head for a while; if it's entirely wrong, and I am to be excoriated, then this forum is as good a place for it as any.
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1. Sex: < Male (0) ... Intersex(5) ... Female (10) >
This is the "physiological / biological" axis; essentially, are your chromosomes XX or XY, and how your plumbing is configured. It's what you're born with. It can be tweaked to an extent with hormones, and surgery can have an effect, but without the technology to completely rewrite a person's DNA, you're kinda stuck with this.
Arnold Schwarzenegger might score around 0. I only have to shave 2 times a week, so I might be about a 2. Consider that Schwarzenegger's use of steroids may have contributed to his score.
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2. Gender: < Masculine (0) ... Neutral (5) ... Feminine (10) >
This is the "psychological / cultural" axis; i.e., a person's gender identity within society. People who are on opposite ends of the sex and gender axes often identify as trans. A tomboy might be classified as "female / masculine". Keep in mind this is a continuum, and knowing someone identifies as cis-female doesn't tell you whether they're a princess who would like to go pony riding, but is terrified she might break a nail (10), or a butch field entomologist who drinks whisky while watching sportsball (2).
I was mistaken for a girl periodically as a child; if you saw a picture, you'd understand why. It still happens to me occasionally. I wear my hair in a braid, and (during the winter) wear a long coat, both which are feminine markers around these parts. Being only 5'7" doesn't help. The mistake typically happens when a store clerk approaches me from behind. It's partly annoying, partly amusing.
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3. Orientation: < Straight(0) ... Bi (5) ... Gay (10) >
This should be self explanatory. One of my pet theories is that there are more people close to the middle of this axis than identify as such; "closeted bisexuals".
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...no wait, I forgot about asexuality. Let's add another axis to cover that.
And isn't axis 3 an oversimplification of orientation? What if someone is sex-straight, but gender-bi? What if I'd rather date the butch field entomologist?
Isn't making masculine / feminine a single axis terribly reductive? There are dozens of factors involved in gender within society, and a simple label doesn't begin to cover it. How do we take into account gender roles that are reversed across different cultures?
Is that a skirt, or is it a kilt?
Wouldn't it be great if we could just let people be who they want, and dispense with labels altogether? I'll have a side-order of World Peace, while you're at it.
Gender identity seems...complicated.