1. A method comprising: performing by one or more computer processors: obtaining a translation of a message in a first language to a second language wherein the translation was submitted by a user; generating a part-of-speech (POS) n-gram representation of the translation comprising a plurality of POS n-grams of two or more different lengths; determining a respective probability for each POS n-gram as a ratio of a count of occurrences of the POS n-gram in a corpus for the second language to a count of all POS n-grams in the corpus having a same length as the POS n-gram; and determining an accuracy of the translation based on a combination of the probabilities.