National Institute of Standards and Technology
NIST (National Institute of Standards and Technology) is a metric for automatic evaluation of machine translation that calculates the similarity between a machine translation output and a reference translation using n-grams precision.
NIST is an adaptation of BLEU.
Compared to BLEU, NIST gives more importance to the less frequent n-grams.
The NIST metric is derived from the BLEU evaluation criterion but differs in one fundamental aspect: instead of n-gram precision, the information gain from each n-gram is taken into account.