Intersexuality is the state of a person whose sex chromosomes, genitalia and/or secondary sex characteristics are determined to be neither exclusively male nor female. A person with intersex may have biological characteristics of both the male and female sexes. A medical definition of intersexuality is "conditions in which chromosomal sex is inconsistent with phenotypic sex, or in which the phenotype is not classifiable as either male or female". Applying this precise definition, the true prevalence of intersex is seen to be about 0.018%.
Research in the late twentieth century has led to a growing medical consensus that diverse intersex physicalities are normal, but relatively rare, forms of human biology. Perhaps the most prominent researcher, Milton Diamond, stresses the importance of care in selection of language related to intersexuality.
“Foremost, we advocate use of the terms "typical," "usual," or "most frequent" where it is more common to use the term "normal." When possible avoid expressions like maldeveloped or undeveloped, errors of development, defective genitals, abnormal, or mistakes of nature. Emphasize that all of these conditions are biologically understandable while they are statistically uncommon.”
The terms hermaphrodite and pseudohermaphrodite, introduced in the 19th century, are now considered problematic. The phrase '"ambiguous genitalia'" refers specifically to genital appearance, but not all intersex conditions result in atypical genital appearance.
Disorders of sex development
The Intersex Society of North America and intersex activists have moved to eliminate the term "intersex" in medical usage, replacing it with "disorders of sex development" (DSD) in order to avoid conflating anatomy with identity. Members of The Lawson Wilkins Pediatric Endocrine Society and the European Society for Paediatric Endocrinology accepted the term "disorders of sex development" (DSD) in their "Consensus statement on management of intersex disorders" published in the Archives of Disease in Children and in Pediatrics. The term is defined by congenital conditions in which development of chromosomal, gonadal, or anatomical sex is atypical. However, this has been met with criticism from other activists who question a disease/disability model and advocate no legal definition of sexes, no gender assignments, no legal sex on birth certificates, and no official sexual orientation categories.
Alternatives to labeling these as "disorders" have also been suggested, including "variations of sex development"