44. A system comprising: one or more memory devices configured store executable instructions; and one or more processors configured to execute the stored instructions to cause the system to: receive a query from a user; identify a multiple word phrase in the query; identify a phrase extension of the identified phrase, wherein the phrase extension of the identified phrase is a sequence of words that begins with the identified phrase but is longer than the identified phrase, and wherein the identified phrase predicts the phrase extension based on a measure of an actual co-occurrence rate of the phrase extension and the identified phrase exceeding an expected co-occurrence rate of the phrase extension and the identified phrase in the document collection; and select documents from the document collection containing the phrase extension.
46. The system of claim 44 , wherein the one or more processors are further configured to execute the stored instructions to cause the system to suggest the phrase extension to the user to use in the query.