When you were mentioning the gender of nouns in the Romance languages, it made me think of some words where the languages don’t even agree. In French it’s La mer but El mar in Spanish. Or El fin in Spanish and La fin in French.My two cents' worth:
Strictly speaking, gender is a phenomonon of language. We see it clearly in Romance languages such as Italian or French. Nouns and pronouns are either masculine or feminine, and verb forms have to agree with the gender of the noun or pronoun. I have more experience with German, which has three genders: masculine, feminine, and neuter. The origin of the gender of some nouns is obvious, but for the life of me, I don't see why, in German, a table is masculine. There may have been, in the murky depths of the language's history, a "sexual" reason for such things. But when the word "magd" (girl), which is feminine, has the diminutive suffix "chen" (little) added to it, it becomes neuter. Go figure.
All this is to say that the very word "gender," which had rigid lines of demarcation in the grammar of languages (I believe there are languages that have more than three genders), had been carried over into discussions of human behavior. I wish we had another word to use besides gender.
Biological sex is, with the rare exceptions of XXY and XYY, binary, with the XX or XY imprinted in every cell of a person's body. Gender, is the sense of a language's structure, is also rigid. That is why we have such confusion when it comes to using a person's preferred pronoun. We are trying to apply something fixed (gender pronouns) to something as fluid as a person's perceptions of themselves and the way they express it in their behavior.
You can see the confusion in that last sentence. In "proper" English usage, I would have used himself instead of themselves, he expresses instead of they express, and his instead of their. In order to express an idea in an acceptable, "non-judgemental" and politically correct way, I've


