Collocations for sex - noun

female, male
opposite
At that age they can start becoming shy with the opposite sex.

same
people of the same sex
same-sex couples/partners
same-sex relationships/marriages/weddings

fair, fairer, gentle, weaker (= women; some women may find these terms offensive)
They tend to consider women as the weaker sex in need of care and protection.

determine
ultrasound tests to determine the sex of a baby
Sex is determined by chromosomal content.

change
For a long time I wanted to change my sex.

be attracted to
to be attracted to the opposite sex

change
to have a sex change
a sex-change operation

equality
issues of sex equality in the office

discrimination, inequality
ratio
difference
The theory predicts sex differences in the brain.

chromosome
the X and Y sex chromosomes

hormone

between the sexes
differences/inequalities/relations between the sexes

the battle of the sexes
The quiz is a battle of the sexes between teams of male and female students.

equality between the sexes, equality of the sexes
on (the) grounds of sex (BrE)
discrimination on grounds of sex

irrespective of sex, regardless of sex
The word ‘man’ can refer to all humans, irrespective of sex.

a member of the opposite sex
This will help us meet attractive members of the opposite sex.

anal, oral, penetrative (esp. BrE), vaginal (esp. AmE)
gay, homosexual, lesbian
heterosexual, straight
good, great, hot, passionate, wild
rough
kinky
safe
Always practise/practice safe sex!

unprotected, unsafe
consensual, non-consensual
extramarital, illicit, premarital
anonymous, casual, promiscuous
group
public (= sex in public places)
explicit, graphic, gratuitous, hard-core, steamy
Movies containing scenes of explicit sex are banned.

Internet, phone
underage, unlawful (BrE)
He was convicted of having unlawful sex with an underage girl.

teen (esp. AmE), teenage

engage in, have
She had never had sex before.

consent to
refuse
get, obtain

life
a healthy sex life

drive, urge
a low sex drive

appeal
Despite his age, he still has a lot of sex appeal.

act
photos showing sex acts

therapist, therapy
partner (esp. AmE)
I have had several sex partners over the years.

organ
education
She is an advocate of abstinence-only sex education. (AmE)
comprehensive sex education (esp. AmE)

scandal
abuse, assault (esp. BrE), attack (BrE), crime, offence/offense
He was arrested for sex crimes.

fiend (informal), offender, pest (BrE,informal)
convicted sex offenders
registered sex offenders

addict, maniac
He had a reputation of being a sex maniac.

film, scene, show
comedy
kitten, symbol
She wants to be known as a singer rather than as a sex symbol.

object
Women are viewed as sex objects and exploited to sell products.

club, shop
aid, toy
industry
worker
In this zone, prostitution is legal, but sex workers must be at least 18.

tourism
trafficking
to crack down on international sex trafficking

slave

sex between
sex between consenting adults

sex with
sex with her husband

sex, drugs and rock 'n' roll (humorous)
sex and violence
sex and violence in today's liberal media

sex outside of marriage
They teach that sex outside of marriage is wrong.

sex sells
Sex sells, the advertisers believe.