Gender = a social-psychological-cultural construct (i.e. all-in-the-mind)
They are not synonyms -- not even close. If you conflate the terms; you will lose every argument on the substantive issues involved. That's 'their' intent -- don't fall for it.
Even when I was 4 I knew that I wanted to play with trucks...that I wanted to play baseball....that I wanted to climb trees and play in the mud. I also knew that I *didn't* want to play with dolls...or put on my Mom's makeup...or wear my Mom's high heels.Nobody had to tell me what I did,or didn't,want.
I call that biological.