It seems to be one of those things that, for people who experience identifying with one category over the other, I’ve seen people report as knowing that that was them when they saw it, even when very young, even if their sex and assigned role at that point was one that was incompatible with either masculinity or femininity. Connecting by role models, imitation and a desire to be able to be those ideals as they saw it were things they could report, the identification of “the same” was something that seemed easiest and amongst the first steps of the brain to carve up the world into categories. There seems to some evidence that some traits normally assigned to either category is inborn to people, and a lot of the ways those traits are displayed, as well as other traits picked up is from culture and upbringing (again in nature vs. nurture debates my answer is that its complicated and the two things intertwine massively, also I’m pretty sure these categories aren’t exclusive by any means).
The best I can offer is that these things are culturally and locale dependant, as well as being open to multiple interpretations. These values are passed down a lot by peoples exposure to them and their wish to satisfy their own identification with those things, often at a young age, and often (in the case of trans people) without realising it. According to Judith Butler (whose theory I’m now going to butcher because its hard to grok) gender as well as things like “masculinity” and “femininity” exist as performance which is not to say those things are acted, faked or not real. Instead that they’re created by peoples actions (deeds mostly, but I think thoughts are slightly okay) and the interactions between them and other people. So masculinity is created by someone being masculine, and their interactions with other masculine people enabling them to recognise that trait in each other.
I think the categories of masculine and feminine also offer another method of bonding and group cohesion which is separate to the categories of male and female. One thing I’ve noticed from attending social events as someone who tends to get read as a slightly feminine man (I once queered up a gazebo, ask me how) is that its quite possible for a group of people of several gender identities to perform masculine actions and bond over those actions, attitudes, cultural norms, etc and another chunk (including overlap sometimes, depending on how policed the group is in terms of trying to push those who are read as being one sex to all go into one group or the other) of the same group can perform feminine actions, etc and socially bond and interact over those.
One reason that trans people seem to get so interested in, and used as examples of, the masculine and feminine is that a number have reported that they they’ve bonded with one category while young, or done their best to learn to act as another category due to denial or being in the cloest. One’s that I’ve read recently have included S. Bear Bergman who has written of hir attempts to be feminine during hir childhood, and the ways in which it frustrated hir that ze couldn’t manage it most of the time, an example of femininity is Kate Bornstein who has written a number books which all include some snippets about her identity, she tried to be manly and masculine but never managed to identify with it that comfortably as far as I can tell, although she managed to perform masculine quite well. The only other option at the time was to be a feminine woman, and while I believe Kate still identifies as feminine I don’t think she identifies purely as the category of woman.
Anyway, I was asked to have a crack at defining masculine and feminine and kind of copped out :) Basically without some srsly heavy thinking I find it pretty hard as a challenge, but I intend to write about how these categories work for me, and how I define them and feel about them myself soon, and I invite everyone to have a go at writing “What does my masculinity and femininity mean to me”, or if you feel you only identify with one of those labels try and write just about that.