Gender-identity/role (coined by John Money to describe gender identity) is expressed through culturally dictated gender roles, like language, clothing, behavior, and other symbols. These terms are defined in most if not all of Money's books, including Gay. Straight, and In-between, and ample examples, such as those discussed below, are also provided.
For example, a traditional gender-identity/role for an American female would begin as an infant. She would learn to call herself a girl, learn to wear dresses, learn to cook and sew, and look forward to adulthood. As an adult woman she would take a "female" occupation, then marry, stay at home, raise children, and maintain the household. In a society that describes these as a woman's role, anyone performing these activities would be judged to be living life as a woman. A male behaving in this way would be running counter to his expected role.
Gender identity is more inclusive than sexual identity. That is to say, the status of one's external genitalia is not the only factor determining whether one identifies oneself as a woman or as a man. For instance, a man who has lost his external genitalia in some accident will not necessarily for that reason cease to regard himself as a man.
Sometimes, for other reasons, a person with external genitalia that appear to be female will have a male gender identity and will act this gender identity out in life using behavior that constitutes a male gender role. Similarly, an individual with external genitalia that appear to be male will have a female gender identity and will act out a female gender role. People who have been made by various social forces to act out a gender role that is not in accord with their gender identity frequently report acute emotional distress as a result. This discomfort is sometimes called gender dysphoria.