The modification of an object which results in the loss of one or more symmetry elements, such as those which preclude @C01058@ (mirror plane, centre of @I03146@, rotation-reflection axis), as in the conversion of a @P04859@ molecular entity into a @C01057@ one.
PAC, 1996, 68, 2193. (Basic terminology of stereochemistry (IUPAC Recommendations 1996)) on page 2205 [Terms] [Paper]