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.