1. A computer-implemented method comprising: obtaining a statistical machine translation model trained using a plurality of question and answer pairs, wherein the model is trained using each question as a source language input and a corresponding answer as a target language input, wherein each question and corresponding answer are in the same natural language; translating, using the statistical machine translation model trained on the plurality of question and answer pairs, a phrase into one or more corresponding translated phrases; and determining one or more synonym pairs by comparing the phrase with the one or more corresponding translated phrases.