number of tokens in the source sentence
number of tokens in the target sentence
average source token length
LM probability of source sentence
LM probability of target sentence
number of occurrences of the target word within the target hypothesis (averaged for all words in the hypothesis - type/token ratio)
average number of translations per source word in the sentence (as given by IBM 1 table thresholded such that prob(t|s) > 0.2)
average number of translations per source word in the sentence (as given by IBM 1 table thresholded such that prob(t|s) > 0.01) weighted by the inverse frequency of each word in the source corpus
percentage of unigrams in quartile 1 of frequency (lower frequency words) in a corpus of the source language (SMT training corpus)
percentage of unigrams in quartile 4 of frequency (higher frequency words) in a corpus of the source language
percentage of bigrams in quartile 1 of frequency of source words in a corpus of the source language
percentage of bigrams in quartile 4 of frequency of source words in a corpus of the source language
percentage of trigrams in quartile 1 of frequency of source words in a corpus of the source language
percentage of trigrams in quartile 4 of frequency of source words in a corpus of the source language
percentage of unigrams in the source sentence seen in a corpus (SMT training corpus)
number of punctuation marks in the source sentence
number of punctuation marks in the target sentence