A search query for a search engine may be improved by incorporating alternate terms into the search query that are semantically similar to terms of the search query, taking into account information derived from the search query. An initial set of alternate terms that may be semantically similar to the original terms in the search query is generated. The initial set of alternate terms may be compared to information derived from the original search query. One example of such information is a set of documents retrieved in response to a search performed using the initial search query. One or more of the alternate terms may be added to the original search query based on their relationship to the information derived from the original search query.