The Levenshtein distance, the standard metric for determining how different words are from each other, can easily be modified to change the penalty for differen

The Levenshtein distance, the standard metric for determining how different words are from each other, can easily be modified to change the penalty for different letter replacements. For example, you can say that the penalty for substituting an 'a' for 's' is 1, and 'a' for 'p' is 10 (or whatever).