1. A method for identifying an entity synonym of an entity in a query log for a search engine, comprising: selecting a first query and a second query from the query log, wherein the query log is stored in a database located on at least one computing device; acquiring a set of Uniform Resource Locators (URLs) that were each selected in response to outputs of the search engine for the first query and that were each selected in response to outputs of the search engine for the second query; measuring a click similarity between the first and second queries based on the acquired set of URLs for the first and second queries; identifying a set of phrase-tag pairs for the first query and a set of phrase-tag pairs for the second query, wherein a tag consists of a selected number of tokens in the query and the phrase is the remaining tokens in the query; measuring a tag similarity between phrase-tag pairs for the first and second queries; determining the first and second queries are synonyms when the click similarity and the tag similarity measurements are each greater than a predetermined threshold value; and storing a query that is determined as a synonym in an entity database located on at least one computing device to enable the query synonym to be associated with the entity.