Various conventions exist for referring to D KL ( P ∥ ∥ Q ) in words. Often it is referred to as the divergence between P and Q, but this fails to convey the fundamental asymmetry in the relation. Sometimes, as in this article, it may be described as the divergence of P from Q or as the divergence from Q to P. This reflects the asymmetry in Bayesian inference, which starts from a prior Q and updates to the posterior P. Another common way to refer to D KL ( P ∥ ∥ Q ) is as the relative entropy of P with respect to Q or the information gain from P over Q.