There were some posts at a male non-Red-Pill sub about the notion of masculinity. I tried to sum it up for them. This is my briefest take.

Esther Vilar in The Manipulated Man defined man and woman in this simple way: Man is a human being who works. A woman, in contrast to man, is a human being who does not work. This was back in the '70s. Thirty years later, she acknowledged that this has changed, of course, since women entered the workforce. What hasn't changed, though, which brings us to the definition of masculinity, is that "only a few of these women would be prepared to offer a life of comfort not only to their children but also the children's fathers, supported by their often substantial salaries."

Psychologist Roy Baumeister, in Is There Anything Good about Men?, again defines masculinity as the capacity to work more than one's individual needs merit, i.e. to provide to others.

These views capture the crux of the matter. In simple terms:

Masculinity is the capacity to love.

Some more discussion to illustrate the point: (please understand it cannot be exhaustive).

As can be seen, the definition of masculinity relies on the definition of love. Love is consciously caring about someone. This ascribes the quality of consciousness to masculinity. If you are doing caring behavior instinctively, that's not bad, but that's neither love nor masculine per se. Every monkey can do that. (Literally). Our definition ascribes the quality of caring to masculinity. This basically means self-sacrifice: if you do "caring" behavior expecting future rewards, you are just being a good businesswoman, not a loving person.

Another example: in several (all?) cultures around the world, "faggot" is a word used for a swindler. People probably can't put their finger to it, why it is so (it isn't that the one who swindled you is having gay sex), but the gist of it is that a swindler diverts resources to himself, instead of caring about you by being honest. Therefore it's about a masculine quality that is subconsciously perceived as lacking about him. (Please note that I'm not necessarily endorsing this view of gay men, only discussing it as a social phenomenon.)

In this example above, we can also see the definition of femininity, which is the opposite of masculinity:

Femininity is the tendency to divert resources towards yourself.

More on that in a while.

Now, the other key word in the definition of masculinity is capacity. This has profound consequences.

For example, if you get incapacitated by disease, women perceive you as less masculine, and you yourself lose your sense of masculinity - unless you can maintain faith that you'll 100% get back on your feet.

Also, capacity is something you can build, consistent with the notion that masculinity is something you develop and cultivate throughout your life.

Confidence is a masculine trait, because it is the subliminal assertion that 1) you needn't count on others for your needs (that's feminine), and 2) you have an abundance on which others can count on.

These notions permeate all discussions around gender issues and men's personal dilemmas. Notably, by actually doing caring behavior as a man, i.e. by incurring the cost, you gradually diminish your capacity for further caring. Women expropriate that in order to branch swing, e.g. after they have depleted the first husbands providing capacity.

Note now that given a man and a woman, a man is generally more probable to be more masculine, but this does not exclude the possibility a woman being more masculine than a man. At the level of politics, however, averages count, not individuals. In most cases, women behaving masculine, i.e. caring for others, is a special case - and ever more rare in contemporary capitalism, despite the fact that women work and earn money themselves.

Now, where did masculinity and femininity come from?

They are neither moral judgments neither "social constructions". They flow quite straightforwardly from the biology of the sexes, from even before humans existed. Females in species, being the only certain parents and the most probable to stick around, had to divert resources to themselves (rather than their children!) since if they perished, their children would perish too. Sadly, women play that biological script even today. Males, on the other hand, evolved displays of abundance as a female attraction trait. Love is a wondrous nature's creation in the male soul.

A practical implication of the above discussion is that men must personally safeguard their capacity to love, since society is build around the tendency (of the system and of women) to exploit that capacity, and in today's society there are no limits to that kind of exploitation.

Tip adam-l for their post.