Adultery

when one spouse has sexual intercourse with a third party. In some states and provinces this is considered grounds for divorce.

Sexual intercourse between a married person and a third party. One of seven fault grounds for divorce is Massachusetts, but rarely used.

Sexual intercourse between a married person and a third party.
Courts once used adultery, once the sole ground for divorce in some jurisdictions, to punish the guilty. Today courts are more interested in the economic impact of adultery, if any, on the marital estate. How much money was spent on the mistress? Think of judges as accountants who want full disclosure and financial accounting for improperly spent funds.