However, if the languages E and F are related and the regular phonetic correspondences between the letter in the two alphabets are known, then we can use P to assign higher likelihood to potential cognates.
we define the prior P (e, f ) to be the probabilistic string-edit distance (Ristad and Yianilos, 1998) between e and f , using the known phonetic correspondences to parameterize the string-edit model.