Abstract: Substrings within strings, such as words within words, are identified based at least in part on recorded behavior of users that have submitted the strings or substrings as search queries. The behavior may relate to actions taken by the users upon having submitting the search queries. The actions may be actions taken in connection with an electronic marketplace, such as actions related to the consumption of items offered in the electronic marketplace. The identified strings and corresponding substrings are used in connection with processing search queries. The strings and substrings may be used to update a search index and/or to modify received search queries for processing.