This might be a stupid question but what the hell are femininity and masculinity? As words they are nouns denoting some kind of essence or quality. What do those essences or qualities consist of. How are they defined? How are they distinguished from one another?
A lot of what is considered "feminine" and "masculine" are social constructs. Things considered feminine are often creative hobbies (like dancing, knitting, sewing, baking), wearing form fitting or flowing clothing, jewelry, and makeup. Being more emotionally sensitive and better at communication is also often associated with femininity. While masculine things are often centered around physicality, like being into sports, hunting, or the military. Masculine clothing is often more squarish and less decorative as well. Another thing that gets a masculine stereotype is video gaming. All of these things fall under gender expression. You can still be a man and like or do "feminine" things, and vice versa. Then there is gender identity, which is the innate sense of maleness or femaleness that someone has. This refers to how you want to be seen and recognized by yourself and society. This includes name and pronouns, and can also have to do with the type of body or sexual characteristics you have or wish to have. This is the reason why trans people transition - to match their gender identity with their sex by taking hormones or having surgery (though some people do not physically transition, and that is okay too). Sometimes gender identity and gender expression get misconstrued and people think they're the same, but they are not. Social conditioning falls heavily into how we perceive gender expression. What things men and women 'typically' do or are into. But even then there are quite a few people who do not fit into those molds.
Like Kodo said above, masculinity and femininity are social constructs - they're ideas of what makes a man a man, and a woman a woman, often based on nothing other than cultural and social expectations. Ideas of what is 'feminine' or 'masculine' varies greatly throughout time, for example, the colour pink is often seen as feminine nowadays, but until the 40s, it was actually considered too 'harsh' a colour for girls, and instead used for boys (whereas girls were assigned the 'softer' colour, blue). But these changes can also be much more recent: skinny jeans were considered very feminine originally, but there are plenty of places in the world where they've simply become the standard for men as well. It also varies greatly depending on culture - something that is considered feminine in the UK may not be considered feminine in Indonesia at all. To take the skinny jeans as example again - here in the nordics they simply started out as being something that's very useful in winter (they keep your legs warmer than baggy jeans do) and there was nothing gendered about them, but in many other countries they came to be considered feminine, for some reason. While masculinity and femininity are often seen as being linked to gender, this is actually rare inherently the case - but becomes the case through the way we're raised and socialised. It is important to recognize that these social constructs are not just random, but are often entangled in gender hierarchies - which is why a lot of the things considered 'feminine' are softer, often suitable for motherhood (being more caring, being more empathetic). Gender hierarchies are actually a lot more complicated than just being masculine-feminine (with different kinds of masculinities and different kinds of femininities at play) but basically these constructed ideas of what it 'means to be a man/woman' are unfortunately still of massive influence on society, even our day-to-day life (like in the case of expected gender roles). That's a discussion for another day, though. But to answer your question, there's no way to define either of them beyond them being social constructs, really. What qualities are feminine or masculine differ per culture, and throughout history, and it's ever changing as well. There's no real, conclusive list of traits belonging to either of these concepts that can be generated.
Thank you for the long and well th ought out replies. I think I was one of those people who never fit the mould growing up. I just sat in this subtle in between place, that was neither masculine or feminine but it wasn't really both either. It's hard to explain, it's kind of like I just grew up without a gender. The only thing I did that was "gendered" by society's standards, was call myself a 'boy.' I hear people saying that the more creative interests are typically considered feminine. My main creative outlet as a child was drawing, and I saw both boys and girls around me liked drawing at an almost equal level, or I perceived it that way. It seemed like the vast majority of my interests growing up were unintentionally gender neutral and no one ever forced me to take up sports or anything like that. I wonder if I would have turned out more "masculine" if someone had pushed me in that direction at an early age. These days I'm into music mostly and I like going for long walks, I also waste a lot of time online none of which seem obviously manly or obviously womanly as far as I'm aware.
