Sentence pair count e 2 9 f 3 e 2 2 f 2 e 1 e 2 1 f 1 f 2 In this way, VB controls the overfitting that would otherwise occur with rare words.
higher values of α can be chosen if smoothing is desired, for instance in the case of the alignment probabilities, which state how likely a word in position i of the English sentence is to align to a word in position j of the French sentence.