= Binary partition bound for relative entropy
{title2=$K(P,Q)\geq d(P(A),Q(A))$}
= Bernoulli reduction of relative entropy
{c}
{synonym}
For a measurable event $A$, applying <Jensen inequality> to $u\log u$ separately on $A$ and its complement shows that the <Kullback-Leibler divergence> between two <probability measures> is at least the divergence between the two event indicators. This reduces a general <probability measure> comparison to a binary one and is the key step in a proof of <Pinsker's inequality>.
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