11. The non-transitory computer-readable storage medium of claim 8 , wherein the substitution rule comprises a rule to substitute a first search query that includes: (i) the phrase that includes the first term, the second term, and the third term, and (ii) the additional, original search query term that is not included in the phrase, with a second search query that includes: (i) the phrase that includes the first term, the second term, and the third term, and (ii) the additional, revised search query term that is different than the additional, original search query term and that is not included in the phrase.
12. The non-transitory computer-readable storage medium of claim 11 , wherein the one or more computers are further configured to perform operations comprising: ranking the first search query and the second search query based at least on (i) a number of times the first search query is submitted to a search engine, and (ii) a number of times that the first search query is followed by the second search query in the collection of search queries.