8. A computer-implemented method comprising: identifying a plurality of queries in a query log, and for each query, one or more search results associated with the query, wherein each search result identifies a corresponding resource and comprises a search result snippet that includes text from the corresponding resource identified by the search result; generating a plurality of query-snippet pairs, wherein each pair associates a respective query of the plurality of queries with a particular search result snippet from one of the search results associated with the query in the query log; training a statistical machine translation model using the plurality of query-snippet pairs, including using each query of each query-snippet pair as a source language input, and a corresponding snippet of the query-snippet pair as a target language input, wherein each query and the search result snippet of each query-snippet pair are in the same natural language; translating, using the statistical machine translation model trained on the plurality of query-snippet pairs and search result snippet pairs, a phrase into one or more corresponding translated phrases; and determining one or more synonym pairs including comparing the phrase with the one or more corresponding translated phrases.
8. A computer-implemented method comprising: identifying a plurality of queries in a query log, and for each query, one or more search results associated with the query, wherein each search result identifies a corresponding resource and comprises a search result snippet that includes text from the corresponding resource identified by the search result; generating a plurality of query-snippet pairs, wherein each pair associates a respective query of the plurality of queries with a particular search result snippet from one of the search results associated with the query in the query log; training a statistical machine translation model using the plurality of query-snippet pairs, including using each query of each query-snippet pair as a source language input, and a corresponding snippet of the query-snippet pair as a target language input, wherein each query and the search result snippet of each query-snippet pair are in the same natural language; translating, using the statistical machine translation model trained on the plurality of query-snippet pairs and search result snippet pairs, a phrase into one or more corresponding translated phrases; and determining one or more synonym pairs including comparing the phrase with the one or more corresponding translated phrases. 9. The method of claim 8 , wherein determining one or more synonym pairs by comparing the phrase with the one or more corresponding translated phrases comprises determining that a term in a particular phrase is different from a corresponding translated term in a particular translated phrase.