sex

sex is on the Basic English 850 List.

servant - sex - shade

sex is one of the 1000 most common headwords.

seven - sex - shall

sex is on the Academic Word List.

Noun

Two people having sex

(uncountable) Sex is an act done by a male and a female (in this case there is sometimes an intent to make babies) or with just two men or women.
- Synonym: sexual intercourse
Most men in our survey say they definitely would not have sex with a new partner without using a condom.
(countable) A person or animal's sex is male, female, or both.
- Synonym: gender
She had not had any male friends during her early life and now found it difficult to talk to members of the opposite sex.