Castration, called orchiectomy in medicine, is the process of rendering ineffective the male organs, such as the testes, which produce spermatozoa and androgenic hormones. In some cases the term has been applied to severing the ovaries from females, although ovariectomy is preferred. While it is most commonly a surgical procedure, "chemical castration" describes suppressing the testicular function with hormones. It also can refer to the effects of trauma that destroy the testes.
The term also may be used for removal of the entire external genitalia, but that is an incorrect technical usage.
Historically, it can happen by the free will of a person who desires to have his testicles removed by surgical methods, but generally the sense is that it is an act against a person's will. Orchiectomy may be performed as a means of palliating cancers that are stimulated by androgens. Chemical or surgical castration is a controversial approach to preventing recidivism by sex offenders.
In Greek mythology, according to Hesiod in Theogony, and as reported by Elizabeth Vandiver, the primordial Greek god Ouranos was castrated by Cronus using a sickle provided by Ouranos' wife, Gaia, and the severed genitals became sea foam which became the goddess Aphrodite.
A boy who is castrated before reaching puberty will have a high voice and fewer muscles and less desire to have sexual intercourse, and be unable to have children or offspring. All persons who are castrated are sterile.
Colloquially, and especially in pet animals, the term "fixing" is used, although it can be argued that the animal's reproductive system was quite functional before it was "broken". Nevertheless, it is common for pets, both to reduce overpopulation, and to change behavior. In cats, "intact" males tend to be more aggressive, mark territory by spraying urine, and are more prone to urogenital disease.