35. A computer-implemented method comprising: receiving a multi-term synonym phrase that is a candidate synonym for a multi-term query phrase; and determining, using one or more computers, that each term of the query phrase is a lexical synonym of a corresponding term of the synonym phrase or shares meaning with the corresponding term of the synonym phrase; in response to determining that each term of the query phrase is a lexical synonym of the corresponding term of the synonym phrase or shares meaning with the corresponding term of the synonym phrase, using the query phrase and the synonym phrase to improve a synonym mapping between a particular term of the query phrase and a term of the synonym phrase that corresponds to the particular term.
51. The method of claim 35 , wherein determining that each term of the query phrase is a lexical synonym of a corresponding term of the synonym phrase or shares meaning with a corresponding term of the synonym phrase comprises: determining that a first term of the query phrase is a lexical synonym of or shares meaning with a first term of the synonym phrase; and determining that a second term of the query phrase is a lexical synonym of or shares meaning with a second term of the synonym phrase.