(countable) Either of two main divisions (either female or male) into which many organisms can be placed, according to reproductive
function or organs.
What Sex is that hamster?
The abnormality is found in both sexes.
(uncountable) The distinguishing property, quality, or assemblage of properties by which organisms are classified as female or male on the basis of their reproductive organs and functions; the set of properties by which male is distinguished from female.
The effect of the medication is dependent upon age, sex, and other factors.
The researchers divided the subjects by sex.
(uncountable) Sexual intercourse; the act of sexual intercourse.
All you ever think about is sex.
We had Sex in the back seat.
(euphemism) Genitalia; a penis or vagina.
(Can we verify(+) this sense?) (dated, with the definite article) the sex.
Women; womankind.
Also, the fair sex, the fairer sex, the whimsical sex.