Gender taxonomy

The gender taxonomy is a classification of the range of different levels at which humans vary in sexual characteristics. It is mainly used by medical specialists working in the area of sex research.^{[citation needed]} John Money and Milton Diamond are probably the best known researchers in this field. Money earned his PhD for research into human hermaphroditism and pseudohermaphroditism, now known as intersex conditions. The taxonomy starts at the simplest, biological level and traces differentiations expressed at the increasingly complicated levels produced over the course of the human life cycle.

• chromosomes (46,XX; 46,XY; 47,XXY ("Klinefelter's syndrome"); 45,X0 ("Turner syndrome"); 47,XYY; 47,XXX ("Triple X syndrome"); XXXX syndrome; XXXXX syndrome, 48,XXYY syndrome, 46,XX/XY mosaic, other mosaic, and others)
• gonads (testes, ovaries, one of each, ovotestes, other types of gonadal dysgenesis)
• hormones (androgens: including testosterone; estrogens, including estradiol, estriol, estrone; antiandrogens and others)
• genitals (primary sexual characteristics — see diagram for the "six class system")
• secondary sexual characteristics (dimorphic physical characteristics, other than primary characteristics)
• brain structure (special kinds of secondary characteristics, due to their influence on psychology and behaviour)
• gender identity (psychological identification with either of the two main sexes)
• gender role (social conformity with expectations for either of the two main sexes)
• erotic preference (gynephilia, androphilia, bisexuality, asexuality and various paraphilias).