Assigned sex in the context of "Birth certificate"

Gender identity is the personal sense of one's own gender. Gender identity can correlate with a person's assigned sex or can differ from it. In most individuals, the various biological determinants of sex are congruent and consistent with the individual's gender identity. Gender expression typically reflects a person's gender identity, but this is not always the case. While a person may express behaviors, attitudes, and appearances consistent with a particular gender role, such expression may not necessarily reflect their gender identity. The term gender identity was coined by psychiatry professor Robert J. Stoller in 1964 and popularized by psychologist John Money.

In most societies, there is a basic division between gender attributes associated with males and females, a gender binary to which most people adhere and which includes expectations of masculinity and femininity in all aspects of sex and gender: biological sex, gender identity, gender expression, and sexual orientation. Some people do not identify with some, or all, of the aspects of gender associated with their biological sex; some of those people are transgender, non-binary, or genderqueer. Some societies have third gender categories.

While in ordinary speech, the terms sex and gender are often used interchangeably, in contemporary academic literature, the terms often have distinct meanings, especially when referring to people. Sex generally refers to an organism's assigned biological sex, while gender usually refers to either social roles typically associated with the sex of a person (gender role) or personal identification of one's own gender based on their own personal sense of it (gender identity).

Most contemporary social scientists, behavioral scientists and biologists, many legal systems and government bodies and intergovernmental agencies such as the WHO make a distinction between gender and sex. In most individuals, the various biological determinants of sex are congruent, and sex is consistent with the individual's gender identity, but in rare circumstances, an individual's assigned sex and gender do not align, and the person may be transgender.