Levenshtein distance
The Word error rate (WER) is a metric based on the Levenshtein distance, where the Levenshtein distance works at the character level, WER works at the word level. It was originally used for measuring the performance of speech recognition systems but is also used in the evaluation of machine translation. The metric is based on the calculation of the number of words that differ between a piece of machine-translated text and a reference translation.