What is Adultery?

Legal Definition
Adultery (anglicised from Latin adulterium) is extramarital sex that is considered objectionable on social, religious, moral, or legal grounds. Though what sexual activities constitute adultery varies, as well as the social, religious and legal consequences, the concept exists in many cultures and is similar in Islam, Christianity 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.

Historically, many cultures have considered adultery as a very serious crime. Adultery often incurred severe punishment, usually for the woman and sometimes for the man, with penalties including capital punishment, mutilation, or torture. Such punishments have gradually fallen into disfavor, especially in Western countries from the 19th century. In most Western countries, adultery itself is no longer a criminal offense, but may still have legal consequences, particularly in divorce cases. For example, in fault-based family law jurisdictions, adultery almost always constitutes a ground for divorce and may be a factor in property settlement, the custody of children, the denial of alimony, etc. Adultery is not a ground for divorce in jurisdictions which have adopted a no-fault divorce model. In some societies and among certain religious adherents, adultery may affect the social status of those involved, and may result in social ostracism.

In countries where adultery is a criminal offense, punishments range from fines to caning and even capital punishment. Since the 20th century, criminal laws against adultery have become controversial, with international organizations calling for their abolition, especially in the light of several high-profile stoning cases that have occurred in some countries. The head of the United Nations expert body charged with identifying ways to eliminate laws that discriminate against women or are discriminatory to them in terms of implementation or impact, Kamala Chandrakirana, has stated that: "Adultery must not be classified as a criminal offence at all". A joint statement by the United Nations Working Group on discrimination against women in law and in practice states that: "Adultery as a criminal offence violates women’s human rights".

In Muslim countries that follow Sharia law, the punishment for adultery may be stoning. There are fifteen countries in which stoning is authorized as lawful punishment; however instances have occurred outside the legal system (extrajudicially). 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. By analogy, in cultures which value and normally practice exclusive interpersonal relationships, sexual relations with a person outside the relationship may also be described as infidelity or cheating, and is subject to sanction.
-- Wikipedia
Legal Definition
A form of extramarital sex between a married person and a person who is not a party to the marriage. In a fault-based divorce scheme adultery is grounds for divorce. In some states, adultery may be a factor in property distribution and/or a maintenance award.
Legal Definition
Criminal law. From ad and alter, another person; a criminal conversation, between a man married to another woman, and a woman married to another man, or a married and unmarriod person. The married person is guilty of adultery, the unmarried of fornicatiou. (q. v.) 1 Yeates, 6; 2 Dall. 124; but see 2 Blackf. 318.

2. The elements of this crime are, 1st, that there shall be an unlawful carnal connexion; 2dly, that the guilty party shall at the time be married; 3dly, that he or she shall willingly commit the offence; for a woman who has been ravished against her will is not guilty of adultery. Domat, Supp. du Droit Public, liv. 3, t. 10, n. 13.

3. The punishment of adultery, in the United States, generally, is fine and imprisonment.

4. In England it is left to the feeble hands of the ecclesiastical courts to punish this offence.

5. Adultery in one of the married persons is good cause for obtaining a divorce by the innocent partner. See 1 Pick. 136; 8 Pick. 433; 9 Mass. 492: 14 Pick. 518; 7 Greenl. 57; 8 Greenl. 75; 7 Conn. 267 10 Conn. 372; 6 Verm. 311; 2 Fairf. 391 4 S. & R. 449; 5 Rand. 634; 6 Rand. 627; 8 S. & R. 159; 2 Yeates, 278, 466; 4 N. H. Rep. 501; 5 Day, 149; 2 N. & M. 167.

6. As to proof of adultery, see 2 Greenl. 40, Marriage.
-- Bouviers Law Dictionary
Legal Definition
Adultery is the voluntary sexual intercourse of a married person with a person other than the offender's husband or wife. Civil Co.de Cal. § 93; 1 Bish. Mar. & Div. § 703; Co.ok v. State, 11 Ga. 53, 56 Am. Dec. 410; State v. Mahan, 81 Iowa, 121, 46 N. W. 855; Banks v. State, 96 Ala. 78, 11 South. 404.

Adultery Is the unlawful voluntary sexual intercourse of a married person with one of the opposite sex, and when the crime is committed between parties, only one of whom is married, both are guilty of adultery. Pen. Code Dak. § 333.

It is to be observed, however, that in some of the states it is held that this crime is committed only when the woman is married to a third person, and the unlawful commerce of a married man with an unmarried woman is not of the grade of adultery. In some jurisdictions, also, a distinction is made between double and single adultery, the former being committed where bath parties are married to other persons, the latter where one only is so married. State v. Fellows, 50 Wis. 65, 6 N. W. 239; State v. Searle. 56 Vt. 516; State v. Lash, 16 N. J. Law, 380, 32 Am. Dec. 397 ; Hood v. State, 56 Ind. 263, 26 Am. Rep. 21; State v. Connoway, Tapp. (Ohio) 90; State v. Weatherby, 43 Me. 258, 69 Am. Dec. 59 ; Hunter v. U. S., 1 Pin. (Wis.) 91, 39 Am. Dec. 277.
-- Black's Law Dictionary
Legal Definition
Sexual intercourse of a married man with a woman not his wife, whether married or single. See 18 L. R. A. (N. S.) 580; also 26 Am. Rep. 21.
-- Ballentine's Law Dictionary