Gender expression typically reflects a person's gender identity (their internal sense of their own gender), but this is not always the case. Gender expression is separate and independent both from sexual orientation and gender assigned at birth. A type of gender expression that is considered atypical for a person's externally perceived gender may be described as gender non-conforming.
In men and boys, typical or masculine gender expression is often described as manly, while atypical or feminine expression is known as effeminate. In girls and young women, atypically masculine expression is called tomboyish. In lesbian and queer women, masculine and feminine expressions are known as butch and femme respectively. A mixture of typical and atypical expression may be described as androgynous. A type of expression that is perceived as neither typically feminine or masculine can be described as gender-neutral or undifferentiated.
The term gender expression is used in the Yogyakarta Principles, which concern the application of international human rights law in relation to sexual orientation, gender identity, gender expression, and sex characteristics.