Syn. -- Adherence, Adhesion. These words, which were once freely interchanged, are now almost entirely separated. Adherence is no longer used to denote physical union, but is applied, to mental states or habits; as, a strict adherence to one's duty; close adherence to the argument, etc. Adhesion is now confined chiefly to the physical sense, except in the phrase "To give in one's adhesion to a cause or a party."