Adultery (from Latin adulterium) is extramarital sex that is considered objectionable on social, religious, moral, or legal grounds. Although the sexual activities that constitute adultery vary, as well as the social, religious, and legal consequences, the concept exists in many cultures and is similar in Christianity, Islam, and Judaism. A single act of sexual intercourse is generally sufficient to constitute adultery, and a more long-term sexual relationship is sometimes referred to as an affair.
In Muslim countries that follow Sharia law for criminal justice, the punishment for adultery may be stoning. There are fifteen countries in which stoning is authorized as lawful punishment, though in recent times it has been legally carried out only in Iran and Somalia. Most countries that criminalize adultery are those where the dominant religion is Islam, and several Sub-Saharan African Christian-majority countries, but there are some notable exceptions to this rule, namely Philippines, Taiwan, and several U.S. states. In some jurisdictions, having sexual relations with the king's wife or the wife of his eldest son constitutes treason.
In the traditional English common law, adultery was a felony. Although the legal definition of adultery differs in nearly every legal system, the common theme is sexual relations outside of marriage, in one form or another.
A marriage in which both spouses agree ahead of time to accept sexual relations by either partner with others is sometimes referred to as an open marriage or the swinging lifestyle. Polyamory, meaning the practice, desire, or acceptance of intimate relationships that are not exclusive with respect to other sexual or intimate relationships, with knowledge and consent of everyone involved, sometimes involves such marriages. Swinging and open marriages are both a form of non-monogamy, and the spouses would not view the sexual relations as objectionable. However, irrespective of the stated views of the partners, extra-marital relations could still be considered a crime in some legal jurisdictions which criminalize adultery.
Children born out of adultery suffered, until recently, adverse legal and social consequences. In France, for instance, a law that stated that the inheritance rights of a child born under such circumstances were, on the part of the married parent, half of what they would have been under ordinary circumstances, remained in force until 2001, when France was forced to change it by a ruling of the European Court of Human Rights (ECtHR) (and in 2013, the ECtHR also ruled that the new 2001 regulations must be also applied to children born before 2001).
The Ten Commandments were meant exclusively for Jewish males. Michael Coogan writes that according to the text the wives are the property of their man, marriage meaning transfer of property (from father to husband), and women are less valuable than real estate, being mentioned after real estate. Adultery is violating the property right of a man. Coogan's book was criticized by Phyllis Trible, who argues that he failed to note that patriarchy was not decreed, but only described by God, patriarchy being specific to people after the fall. She states that Paul the Apostle made the same mistake as Coogan.
According to Muhammad, an unmarried person who commits adultery or fornication is punished by flogging 100 times; a married person will then be stoned to death. A survey conducted by the Pew Research Center found support for stoning as a punishment for adultery mostly in Arab countries; it was supported in Egypt (82% of respondents in favor of the punishment) and Jordan (70% in favor), as well as Pakistan (82% favor), whereas in Nigeria (56% in favor) and in Indonesia (42% in favor) opinion is more divided, perhaps due to diverging traditions and differing interpretations of Sharia.
The Kamasutra, states Ludo Rocher, discusses adultery and Vatsyayana devotes "not less than fifteen sutras (1.5.6–20) to enumerating the reasons (karana) for which a man is allowed to seduce a married woman". According to Wendy Doniger, the Kamasutra teaches adulterous sexual liaison as a means for a man to predispose the involved woman in assisting him, working against his enemies and facilitating his successes. It also explains the many signs and reasons a woman wants to enter into an adulterous relationship and when she does not want to commit adultery. The Kamasutra teaches strategies to engage in adulterous relationships, but concludes its chapter on sexual liaison stating that one should not commit adultery because adultery pleases only one of two sides in a marriage, hurts the other, it goes against both dharma and artha.
Buddhism considers celibacy as the monastic ideal. For he who feels that he cannot live in celibacy, it recommends that he never commit adultery with another's wife. Engaging in sex outside of marriage, with the wife of another man, with a girl who is engaged to be married, or a girl protected by her relatives (father or brother), or extramarital sex with prostitutes, ultimately causes suffering to other human beings and oneself. It should be avoided, state the Buddhist canonical texts.