1. A computer-implemented method for generating a synonym list from an existing thesaurus, the method comprising: preparing a first feature vector from a natural language query and preparing a second feature vector from a result of the natural language query; determining, using a processor, whether a combination of a first feature from the first feature vector and a second feature from the second feature vector is included as a synonym pair in the existing thesaurus; and generating the synonym list by adding the combination to the synonym list when the determination is positive.