<Li> Dominus Noster ("Our Lord"): an honorific title; the praenomen of later emperors . </Li> <Li> Imperator ("Commander" or "Commander - in - Chief"): a victory title taken on accession to the purple and after a major military victory </Li> <Li> Imperator Destinatus ("Destined to be Emperor"): heir apparent, used by Septimius Severus for Caracalla </Li> <Li> Invictus ("Unconquered"), an honorific title . </Li>

What was the heir to the roman empire called