Well...I'm never going to forget the Vietnamese word for "complicated"!
and happiness "hanh phuc"
Hah, took me a minute! I'm never going to forget it now either!
how do we know this is "women" rather then "the woman"
I believe because there is no classifier, that is, "the woman" would be "người phụ nữ".
According to a native speaker it is because there is no classifier. This makes it a general statement and in English you would express that by using the plural.
Phụ nữ luôn luôn đúng :D