Sexologist?John Money?is often regarded as the first to introduce a?terminological distinction?between biological sex and "gender role" (which, as originally defined, includes the concepts of both gender role and what would later become known as gender identity) in 1955[8][9]?although?Madison Bentley?had already in 1945 defined gender as the "socialized obverse of sex",[10][11]?and?Simone de Beauvoir's 1949 book?The Second Sex?has been interpreted as the beginning of the distinction between sex and gender in?feminist theory.[12][13]