the operation of cutting away all or part of the foreskin (prepuce) of the penis. The origin of the practice is unknown, although the widespread distribution of circumcision as a ritual suggests great antiquity. Circumcision is generally viewed by anthropologists (anthropology) as a practice through which various aspects of social identity are inscribed upon the human body, such as gender (gender identity), purity (purification rite), or social or sexual maturity.

While most scholars agree on these generalities, the specific timing, meanings, and rites associated with circumcision have varied greatly over time and space. In ancient Egypt (Egypt, ancient), boys were generally circumcised between ages 6 and 12. Among Ethiopians, Jews (Judaism), some Muslims, and some other groups, the operation is performed shortly after birth or perhaps a few years after birth. Some Arab groups traditionally perform the operation immediately before marriage. Among most other peoples who practice it ritually, circumcision is performed at puberty as a passage rite.

In many cultures, circumcision is also regarded as being of profound religious significance. In Judaism, for instance, it represents the fulfillment of the covenant between God and Abraham (Genesis 17:10–27), the first divine command of the Pentateuch—that every male child shall be circumcised. That Christians (Christianity) were not obliged to be circumcised was first recorded biblically in Acts 15.

Medically, the operation consists of the cutting of the foreskin to allow its free retraction behind the glans penis (the conical head). The foreskin consists of a double layer of skin that, without circumcision, more or less completely covers the glans penis. Under the inner layer of foreskin there are situated a number of glands that secrete a cheeselike substance called smegma. Accumulation of smegma beneath the foreskin may result in great discomfort and may serve as the source of a rather penetrating odour if cleanliness and hygiene are not observed.

In Western countries, circumcision became increasingly common during the 19th century because the medical establishment defined it as a hygienic procedure. By the closing decades of the 20th century, it had generally fallen out of favour except in cases of medical or religious necessity. The United States proved to be the exception to this trend; in the early 21st century most boys there continued to be circumcised shortly after birth, at least in cases where there were no compelling reasons for delay. A U.S. countercircumcision movement gained credence in 1971 when the American Academy of Pediatrics found that there was “no absolute medical indication for routine circumcision.”

Advocates of circumcision cite studies indicating that circumcised men have a lower incidence of AIDS, syphilis, and other sexually transmitted diseases (sexually transmitted disease) than uncircumcised men. In addition, their female partners have a lower risk of cervical cancer. In 2007 the World Health Organization (WHO) reviewed several studies of human immunodeficiency virus (HIV) in men living in Africa and found that male circumcision reduced their risk of heterosexually acquired infection by significant amounts (ranging from 48 to more than 60 percent). The resulting WHO report recommended that circumcision become a standard tool within comprehensive programs for the prevention of HIV, but also cautioned that:

Researchers have issued two important cautionary statements about these findings. First, their results are specific to heterosexual activity, and circumcision may not be protective for those engaging in homosexual intimacy. Second, the opposite findings apply to the practice sometimes known as female circumcision, also called female genital cutting (FGC), which is more likely to increase the rate of HIV transmission than to reduce it.