1. A method for search string expansion, the method comprising: receiving a list of reserved phrases, each reserved phrase in the list being related to a content and wherein each string is associated with a portion of the content; categorizing each reserved phrase according to linguistic characteristics; generating a candidate list of synonyms for each reserved phrase in the list; filtering the candidate list of synonyms by: removing synonym duplicates; and comparing synonyms to a synonym rule and removing synonym that do match the synonym rule; and categorizing each synonym according to linguistic characteristics of the associated reserved word.