A transsexual person is someone who experiences a gender identity that is inconsistent with their assigned sex, and desires to permanently transition to the sex or gender with which they identify, usually seeking medical assistance (including gender affirming therapies, such as hormone replacement therapy and gender affirming surgery) to help them align their body with their identified sex or gender. The term transsexual is a subset of transgender, but some transsexual people reject the label of transgender.: 8, 34, 120–121  A medical diagnosis of gender dysphoria can be made if a person experiences marked and persistent incongruence between their gender identity and their assigned sex. Understanding of transsexual people has rapidly evolved in the 21st century; many 20th century medical beliefs and practices around transsexual people are now considered outdated. Transsexual people were once classified as mentally ill and subject to extensive gatekeeping by the medical establishment, and remain so in many parts of the world..