The voluntary sexual intercourse by a married person with someone other than his or her spouse. The consent of both parties and penetration are required for adultery to exist. Under the common law, only a married woman could commit adultery, but most states now apply the term to married men as well. Also, in the states where adultery is still a crime, most statutes now provide that the unmarried sexual partner of a married person can also be charged with the offense. See also criminal conversation, fornication, and rape.