"Gender", in common usage, refers to the differences between men and women. Encyclopaedia Britannica notes that gender identity is "an individual's self-conception as being male or female, as distinguished from actual biological sex." Although "gender" is commonly used interchangeably with "sex," within the academic fields of cultural studies, gender studies and the social sciences in general, the term "gender" often refers to purely social rather than biological differences. Some view gender as a social construction rather than a biological phenomenon. People whose gender identity feels incongruent with their physical bodies may identify themselves as intersex, transgender or genderqueer.
Many languages have a system of grammatical gender, a type of noun class system — nouns may be classified as masculine or feminine (for example Spanish, Hebrew, Arabic and French) or may also have a neuter grammatical gender (for example Sanskrit, German and Polish). In such languages, this is essentially a convention, which may have little or no connection to the meaning of the words. Likewise, a wide variety of phenomena have characteristics termed gender, by analogy with male and female bodies (such as the gender of connectors and fasteners) or due to societal norms.