Adultery, or marital infidelity is generally defined as consensual sexual intercourse by a married person with someone other than their lawful spouse.
As there is usually an implicit or explicit agreement between spouses to not have sex outside the marriage, the common synonym for adultery is infidelity as well as unfaithfulness or in colloquial speech, cheating.
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Adultery, Cheating Spouse Help Top PI Bill Mitchell is an infidelity expert. He is a nationally known guest of TV, radio and newsprint media.