sex

sex — noun

1. the physical characteristic that makes a living thing male or female, based on b

1.nounA2
Definition

the physical characteristic that makes a living thing male or female, based on body parts, chromosomes, and hormones present from birth

Example

The doctor recorded the baby's sex on the birth certificate at the hospital.

collocation: baby's sex

On the form, each student circled whether their sex was male or female.

Common collocations
  • baby's sex
  • sex of the child
  • biological sex
  • determine the sex
  • change sex
  • opposite sex
Synonyms
  • gender

    broader term that includes social and cultural identity, not just biology

  • biological sex

    explicitly distinguishes from gender identity

Usage Note

This sense refers to biological traits at birth. Distinguish from noun/4 (CATEGORY DIVISION), which focuses on the classification system rather than the physical state itself.

Common Mistakes

Could you tell me your sex on this form?' (too direct).
Please indicate your sex on this form.
'Indicate' is the standard polite verb on forms.

2. all people who are male, or all people who are female, thought of as a single gr

2.nounB2
Definition

all people who are male, or all people who are female, thought of as a single group

Example

The law forbids discrimination against any person on the basis of sex.

collocation: discrimination on the basis of sex

The study compared how the two sexes perform in science and mathematics at school.

collocation: the two sexes

Common collocations
  • the sexes
  • both sexes
  • the opposite sex
  • the same sex
  • on the basis of sex
  • sex discrimination
Synonyms

Usage Note

Always used with 'the' before 'sex' or a determiner like 'both' ('both sexes', 'the sexes'). Common in formal, legal, and academic writing.

Common Mistakes

Sex discrimination is illegal' (vague).
Discrimination on the basis of sex is illegal in most countries.
The longer form is the standard legal phrasing.

3. physical activity that involves the touching of sexual body parts, especially be

3.nounB1
Definition

physical activity that involves the touching of sexual body parts, especially between two people as part of an intimate relationship

Example

The movie contains scenes of sex and violence and is not suitable for children.

register: formal warning context

The school's health class covers topics such as safe sex and how to prevent disease.

collocation: safe sex

Common collocations
  • have sex
  • safe sex
  • sex before marriage
  • sex education
  • casual sex
  • talk about sex
Synonyms

Usage Note

Frequently used without an article in general discussions. Contrast with noun/1 (BIOLOGICAL STATE) and noun/5 (SEXUAL FEELINGS) — this sense describes the physical act itself.

Common Mistakes

They did sex' (direct translation from some languages).
They had sex.
The verb collocation is always 'have sex' in English.

4. a category that a living thing belongs to, either male or female, based on how i

4.nounB1
Definition

a category that a living thing belongs to, either male or female, based on how it produces babies

Example

On the application form, please indicate your sex by ticking one of the boxes provided.

The vet said the sex of young rabbits is hard to tell just by looking.

collocation: sex of [animal]

Common collocations
  • sex of [plant/animal]
  • determine the sex
  • regardless of sex
  • sex category
Synonyms
  • gender

    increasingly preferred for humans, though gender includes identity beyond biology

  • sex category

    explicitly marks this as a classification concept

Usage Note

This sense names the classification system itself rather than describing a physical state (use noun/1 for that) or a social group (use noun/2). Frequently paired with 'of' to link an organism to its category.

5. the natural human interest in sex, including feelings of desire, thoughts about

5.nounB2
Definition

the natural human interest in sex, including feelings of desire, thoughts about sex, and how people express themselves sexually

Example

Hollywood movies are full of sex and glamour designed to draw large audiences.

register: entertainment/media context

The advertising campaign used sex to sell everything from perfume to sports cars on television.

collocation: sex sells

Common collocations
  • sex and glamour
  • sex sells
  • sex and violence
  • love and sex
  • full of sex
Synonyms
  • sexuality

    broader term encompassing identity, orientation, and expression

  • sexual desire

    focuses on the feeling aspect

  • eroticism

    more formal, often associated with art and literature

Usage Note

This sense describes the psychological and cultural dimension of sex rather than the physical act (noun/3). Common in discussions about media, advertising, and social attitudes.

sex — verb

Word family

  • sexual
    adjectiveB1
  • sexy
    adjectiveA2
  • sexuality
    nounB2
  • sexism
    nounB2
  • sexist
    adjectiveB2
  • sexed
    adjectiveC1
  • unisex
    adjectiveB2
  • intersex
    adjectiveC1
  • bisexual
    adjectiveB2
  • homosexual
    adjectiveB2
  • heterosexual
    adjectiveB2

Synonym discussion

Sense: noun/1

Sex and gender are often used interchangeably in everyday speech, but they carry important differences. Sex (in sense 1) refers to the biological state — chromosomes, hormones, and anatomy — that a person is born with. Gender, by contrast, describes the social and cultural roles, behaviors, and identities that a society associates with being male or female. For example, a doctor might ask 'What sex is the baby?' after delivery (biology), but a researcher might study 'gender differences in career choices' (social roles). The term 'biological sex' is used when the speaker wants to explicitly distinguish the physical reality from gender identity. Learners should be careful: using 'sex' where 'gender' is expected can sound outdated or insensitive in some contexts, particularly in formal or academic writing about human identity.

sex ↗gender ↗biological sex

Common collocations

Nouns

  • education (sex education)
  • appeal (sex appeal)
  • life (sex life)
  • discrimination (sex discrimination)
  • offender (sex offender)
  • drive (sex drive)

Phrases

Prepositions

  • of (the sex of the baby)
  • between (between the sexes)
  • with (have sex with)
  • before (sex before marriage)

Etymology

LatinFrenchEnglish

Sex comes from Latin 'sexus,' meaning 'the condition of being male or female.' The word moved into English through Old French 'sexe' around the 1300s. The modern sense of physical sexual activity ('have sex') developed in the early 1900s, while the verb senses ('to sex an animal' and 'to sex up') appeared in the 1900s as specialized extensions.