21. The system of claim 19 , the operations further comprising: identifying a candidate synonym for the particular query term in context with an adjacent query term of the original search query that is adjacent to the particular query term in the original search query; and determining that, in the stored data that specifies, for the pair of terms that includes the particular query term and the candidate synonym of the particular query term, a confidence value for the ether adjacent query term does not satisfy a threshold.
22. The system of claim 21 , the operations further comprising: determining, in the context of the adjacent query term to the particular query term, that the candidate synonym is a definitive non-synonym for the particular query term; and determining not to revise the original search query, based on determining that the candidate synonym is a definitive non-synonym for the particular query term.