Sex and gender are different concepts that are often used interchangeably. The UK government refers to sex as being biologically defined, and gender as a social construct that is an internal sense of self, whether an individual sees themselves as a man or a woman, or another gender identity.

In general terms, sex refers to a person’s physical characteristics at birth, and gender encompasses a person’s identities, expressions, and societal roles.

A person may identify with a gender that is different from their natal sex or with no gender at all. The latter identity is often referred to as nonbinary, but this is an umbrella term that covers many identifications.