Traditionally, an oath (from Anglo-Saxon āþ, also a plight) is a statement of fact or a promise taken by a sacrality as a sign of verity. A common legal substitute for those who object to making sacred oaths is to give an affirmation instead. Nowadays, even when there is no notion of sanctity involved, certain promises said out loud in ceremonial or juridical purpose are referred to as oaths. "To swear" is a verb used to describe the taking of an oath; to make a solemn vow. Source: Wikipedia (en)