Any artistic element of a coat of arms which does not change the nature of those arms is referred to as an Accident.
Historically a good deal of latitude was given to heraldic artists in their depiction of a particular coat of arms. Minor differences in how a charge was drawn, its exact position or attitude all had a good deal of “wiggle room” so long as the depicted arms would still be accurately described with the same blazon.
A comprehensive term applying to marks of difference and the like, as well as any artistic interpretations of the arms in emblazon which do not substantively alter the nature or blazon of the arms. An additional mark on a coat of arms, which may be retained or eliminated without altering its essential character.