Journal article: We first prove the noteworthy fact that Central Dominance with m=1 (CD1), introduced by Gollier (1995), is a particular case of Second order Stochastic Dominance. We then introduce a new tractable class of dominance that we name Relative order and we prove that this class is a strict subclass of CD1. Finally, we show that some known classes of dominance are particular cases of our new class of dominance.