The likelihood of a piece of evidence according to a hypothesis $H,$ known as "the likelihood of $e$ given $H$ ", is often written either $L_{e} (H)$ or $L (H ∣ e) .$ The latter notation is confusing, because then $L (H ∣ e) = P (e ∣ H) .$ Many students of statistics find it hard enough to keep the difference between $P (H ∣ e)$ and $P (e ∣ H)$ straight in their heads if we don't occasionally swap the order of the arguments when talking about similar functions, so on Arbital, we much prefer the notation $L_{e} (H) = P (e ∣ H) .$

Make this a child of 'likelihood' when 'likelihood' exists.

Likelihood notation