Sex refers to the biological categories — male, female, intersex — defined by anatomy, hormones and chromosomes: "the study recorded the sex of each participant". Gender refers to the social and personal dimension: roles, expression and how someone identifies — "the survey asked which gender they identified with". In everyday speech the two are frequently used interchangeably, even where the distinction is meant to apply.
The distinction as it is drawn
Across medicine, psychology and academic style guides, sex is the biological term and gender the social one. A birth record, a clinical trial's inclusion criteria and a species description all deal in sex. A discussion of expectations, roles, presentation or identity deals in gender.
- "Male mice were used because the drug's effect varies by sex."
- "The report examines the gender pay gap in the sector."
- "Applicants may state their gender or leave the field blank."
The test to apply
Ask what your sentence actually turns on. If the point is anatomy, chromosomes, reproduction or physiology — something a laboratory or a doctor would measure — write sex. If the point is identity, roles, stereotypes, language or how someone is treated and addressed, write gender. If a sentence works with either, you are probably in ordinary usage where the choice will not be read closely.
How the words are really used
Be honest about the gap between the rule and the street. In general English, gender has for decades served as a polite substitute for sex, largely because sex also means sexual activity and is awkward on a form. That is why countless documents ask for your "gender" and expect only "male" or "female" — a question about sex wearing the other word's label. Careful writers observe the distinction; ordinary usage often does not, and neither the confusion nor the substitution is new.
Where precision matters — research writing, medical records, policy documents, legal drafting — the distinction is enforced and worth respecting. In casual prose, forcing it can sound stilted.
A separate meaning to keep clear
In linguistics, gender means something else entirely: the grammatical classes that nouns fall into in languages such as French, German or Spanish, conventionally labelled masculine, feminine and neuter. German das Mädchen ('the girl') is grammatically neuter, which shows how little grammatical gender has to do with people.
Related words
Gender identity is a person's own sense of their gender. Gender expression is how that is presented outwardly through dress, name, voice and manner. Sex also functions as a verb in specialist contexts, as in sexing chicks. Choose the narrowest accurate term rather than the fashionable one, and define it if your document depends on the difference.
Frequently Asked Questions
Should a form ask for gender or sex?
It depends on what the data is for. A clinical form that needs biological information should ask for sex; an HR or membership form recording how someone identifies should ask for gender. Many forms ask for gender and offer only male and female, which mixes the two.
Are gender and sex interchangeable in normal writing?
In everyday English they are widely swapped, and readers rarely object. In medical, scientific, legal or policy writing they are treated as separate terms and should not be substituted for each other.
What does gender mean in grammar?
It refers to noun classes in languages such as Spanish or German — masculine, feminine, neuter — which control article and adjective agreement. It is unrelated to the sex or identity of any person.