If we assume that S X and S Y are similar to each other in the LM's representation space, then A(Y | X) > 0 -i.e., encountering sentences with S X causes the LM to assign a higher probability to sentences with S Y .
if we assume that S X and S Y are unrelated to each other, then A(Y | X) = 0 -i.e., encountering sentences with S X does not cause the LM to change its probability for sentences with 3 A is shorthand for adaptation.