17. A non-transitory computer-readable storage device storing instructions that, when executed by data processing apparatus, cause the data processing apparatus to perform operations comprising: receiving a query submitted by a user to a search engine, wherein the query includes a first compound term; and in response to receiving the query, performing the following operations: generating one or more splits of the first compound term, wherein each split divides the compound term into two or more subterms, wherein at least one subterm is a term in a dictionary that associates terms with scores derived from a respective frequency of use of the subterm; assigning a score to one or more subterms of each split that are in the dictionary, wherein the score for a subterm is the score stored in the dictionary for the subterm; determining an overall score for each split from the scores for the subterms of the split; selecting one or more of the one or more splits according to the overall score for each split; and augmenting the query with the subterms of each selected split.
21. The non-transitory computer-readable storage device of claim 17 , wherein the operations further comprise receiving a list of fugenmorphemes for a first language corresponding to a language of the first compound, wherein each fugenmorpheme is a letter that is added between subterms when creating a compound term in the first language, wherein at least one of the one or more splits omits a fugenmorpheme on the list of fugenmorphemes from the subterms of the split.