1. A phrase analysis system comprising: a phrase database configured to store phrases; and a phrase analysis computer coupled with the phrase database and configured to: obtain a corpus comprising a plurality of phrases; extract phrases from the corpus; determine a degree of similarity among the phrases based on phrase contexts associated with the phrases and on overlaps among phrase contexts determined by surrounding phrases in the corpus proximate to the phrases; and cluster the phrases into classes within the phrase database based on the degree of similarity among the phrase.