sex

noun

1
activities associated with sexual intercourse
they had sex in the back seat
2
the properties that distinguish organisms on the basis of their reproductive roles
she didn't want to know the sex of the foetus
3
all of the feelings resulting from the urge to gratify sexual impulses
he wanted a better sex life
the film contained no sex or violence
4
either of the two categories (male or female) into which most organisms are divided
the war between the sexes

Also useful for “sex”:Scrabble— High-value letters — see what it scores