Transsexual people experience a gender identity that is inconsistent with their assigned sex, and desire to permanently transition to the sex or gender with which they identify, usually seeking medical assistance (including sex reassignment therapies, such as hormone replacement therapy and sex reassignment 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. A medical diagnosis of gender dysphoria can be made if a person experiences marked and persistent incongruence between their experienced gender — their personal sense of their own gender — and their assigned sex. Understanding of transsexuality has changed very quickly in the 21st century. Many 20th century medical beliefs and practices around transsexuality are now considered deeply outdated. It was once classified as a mental disorder and subject to extensive gatekeeping by the medical establishment, and remains so in much of the world. Terminology
Transsexual has had different meanings throughout time. In modern usage, it refers to "a person who desires to or who has modified their body to transition from one gender or sex to another through the use of medical technologies such as hormones or surgeries." It is considered an antiquated term, and is sometimes pejorative. The general shift is to instead use the term transgender or the abbreviated form trans, but due to its historical usage, transsexual remains in the modern vernacular. : 742–744  In understanding the subject, it is noted that there is a difference between gender and sex.
The similar specifiers attracted to men, attracted to women, attracted to both or attracted to neither were used in the DSM-IV.Many transsexual people choose the language of how they refer to their sexual orientation based on their gender identity, not their birth assigned sex. Surgical status
Several terms are in common use, especially within the community itself relating to the surgical or operative status of someone who is transsexual, depending on whether they have already had sex reassignment surgery (SRS), have not had SRS but still intend to, or do not intend to have SRS. They are, post-op, pre-op, and non-op, respectively. Pre-operative
A pre-operative transsexual person, or simply pre-op for short, is someone who intends to have SRS at some point, but has not yet had it. Post-operative
A post-operative transsexual person, or post-op for short, is someone who has had SRS. Non-operative
A non-operative transsexual person, or non-op, is someone who has not had SRS, and does not intend to have it in the future. There can be various reasons for this, from personal to financial. Having SRS is not a requirement of being transsexual. Evolutionary biologist and trans woman Julia Serano criticizes the societal preoccupation with SRS as phallocentric, objectifying of transsexuals, and an invasion of privacy. : 229–231

Historical understanding
Transgender people are known to have existed since ancient times. A wide range of societies had traditional third gender roles, or otherwise accepted trans people in some form.