Gender is defined as a "set of social, cultural, and linguistic norms that can be attributed to someone’s identity, expression, or role as masculine, feminine, androgynous, or nonbinary." Sex is defined as being "assigned at birth by medical professionals based on the appearance of genitalia, and related assumptions about chromosomal makeup, gender identity, expressions, and roles emerge over the life span, sometimes changing over time. ": 277–278

Origins
Norman Haire reported that in 1921 Dora R of Germany began a surgical transition, under the care of Magnus Hirschfeld, which ended in 1930 with a successful genital reassignment surgery (GRS). In 1930, Hirschfeld supervised the second genital reassignment surgery to be reported in detail in a peer-reviewed journal, that of Lili Elbe of Denmark. In 1923, Hirschfeld introduced the (German) term "Transsexualismus", after which David Oliver Cauldwell introduced "transsexualism" and "transsexual" to English in 1949 and 1950.Cauldwell appears to be the first to use the term to refer to those who desired a change of physiological sex. In 1969, Harry Benjamin claimed to have been the first to use the term "transsexual" in a public lecture, which he gave in December 1953. Benjamin went on to popularize the term in his 1966 book, The Transsexual Phenomenon, in which he described transsexual people on a scale (later called the "Benjamin scale") of three levels of intensity: "Transsexual (nonsurgical)", "Transsexual (moderate intensity)", and "Transsexual (high intensity)".
Other self-identified transsexual people state that those who do not seek sex reassignment surgery (SRS) are fundamentally different from those who do, and that the two have different concerns, but this view is controversial, and others argue that merely having some medical procedures does not have such far-reaching consequences as to put those who have them and those who have not (e.g. because they cannot afford them) into such distinctive categories. Some have objected to the term transsexual on the basis that it describes a condition related to gender identity rather than sexuality. For example, Christine Jorgensen, the first person widely known to have sex reassignment surgery (in this case, male-to-female), rejected transsexual and instead identified herself in newsprint as trans-gender, on this basis.The trans community has generally taken issue with the term transsexual because it over-medicalizes the trans experience, and focuses too much on diagnosis. : 743  The term transgender emerged in part in an attempt to break the "medical monopoly" on transitioning that transsexual implied. GLAADs media reference guide offers the following distinction on the use of transsexual:An older term that originated in the medical and psychological communities. As the gay and lesbian community rejected homosexual and replaced it with gay and lesbian, the transgender community rejected transsexual and replaced it with transgender. Some people within the trans community may still call themselves transsexual. Do not use transsexual to describe a person unless it is a word they use to describe themself.