A man, or a woman are expression of the gender identity of a person in relationship to the gender expression associated with man or woman in society.
In short, you identify as a man if your gender identity is similar to the gender expression of the men in society.
Yes, I'm starting to feel it.
DO you have a scientific source for that ?
Yes and it doesn't make nature binary.. You are just projecting a freudian wet dream on reality, that's all.