Unlike some

Unlike some other sexual activities, vaginal intercourse has rarely been made taboo on religious grounds or by government authorities, as procreation is inherently essential to the continuation to the species or of any particular genetic line, which is considered to be a positive factor, and indeed, enables most societies to continue in the first place. Many of the cultures that had prohibited sexual intercourse entirely no longer exist; an exception is the Shakers, a group that reached a size of about 6,000 full members in 1840, but as of 2009 had only three members left.^[34] There are, however, many communities within cultures that prohibit their members to engage in any form of sex, especially members of religious orders and the priesthood in the Roman Catholic Church and Mahayana Buddhist monks. Within some ideologies, coitus has been considered the only "acceptable" sexual activity. Relatively strict designations of "appropriate" and "inappropriate" sexual behavior have been defined by human cultures for thousands of years. These legal or cultural restrictions may include:

• Sex among partners who are not married (this is sometimes referred to as fornication)
• Sex between a married person and someone to whom they are not married (called adultery or extramarital sex).
• Sex between partners of the same sex (also called homosexuality).
• Commercial sex (also called prostitution).
• Sex between a living human and a human corpse (also called necrophilia).
• Sex between close relatives (also called incest).
• Adults having sex with children (depending on the country and its laws, also called child sexual abuse)
• Humans having sex with non-human animals (also called bestiality).
• Sex acts other
• Sex between members of different tribes, ethnic groups, or races, as in South Africa or the United States during periods of racial segregation (also called miscegenation).
• than vaginal intercourse (including oral sex or anal sex, both sometimes called Sodomy).
• Sex, or pre-sexual behavior or communication inviting sex, in a public place (also called public indecency, or lewd and lascivious behavior).
• Depictions of sex in print or video (also called pornography).
• Touching a woman illicitly (also called "outraging the modesty of a female"^[35]).
• Sexual intercourse that is te
• Sexual intercourse during a woman's menstrual period, as seen in Judaism.
• rminated by the man before ejaculation, or results in ejaculation outside the vagina, as seen in ancient Judaism (also called coitus interruptus, or Onanism).
• Sexual touching of one's self (also called masturbation, or Onanism).

Often a community adapts its legal definitions during case laws for settling disputes. For example, in 2003 the New Hampshire Supreme Court ruled that same-sex relations do not constitute sexual intercourse, based on a 1961 definition from Webster's Third New International Dictionary, in Blanchflower v. Blanchflower, and thereby an accused spouse in a divorce case was found not guilty of adultery based on this technicality.

Most countries have age of consent laws specifying the minimum legal age for engaging in sexual intercourse. Sexual intercourse with a person against their will, or without their informed legal consent, is referred to as rape, and is considered a serious crime in most countries. Some countries codify as rape any sex with mentally handicapped persons of any age. Sex, regardless of consent, with a person under the age of consent is often considered to be sexual assault or statutory rape. The age of consent varies from country to country and often by state or region; commonly, the age of consent is set anywhere between twelve and eighteen years of age, with sixteen years being the most common age the law sets. Sometimes, the age of consent is lowered for people near the same age wishing to participate in intercourse. For example, in Canada, the minimum age of consent for all couples is 16. However, the age of consent can go below 16 on the condition that the couple still are not two years of age apart. Religions may also set differing ages for consent, with Islam setting the age at puberty, which can vary from around 10 to 14. There are often further restrictions on age concerning anal sex, homosexual sex, or sex with someone in a position of trust or authority, such as a teacher or caretaker.

Though there are exceptions, most non-Islamic and multi-cultural countries no longer criminalize consensual sex of any sort among adults. In contrast, Islamic countries typically imprison or execute homosexuals. Iran alone is estimated to have executed 4,000 persons for homosexual sex since the Islamic Revolution of 1979, including two teenage boys in 2005.^[36]