1. A method for completing a question comprising: receiving, from a user, a question prefix representing a portion of a natural language question; selecting, based on the question prefix, at least one index comprising a short text index or a question term index, the short text index comprising a plurality of text entries, each entry corresponding to an associated document, the question term index comprising a plurality of question entries, each entry corresponding to a partial question phrase; searching the selected at least one index using the question prefix and retrieving a plurality of retrieved entries; selecting a subset of the plurality of retrieved entries; responsive to selecting the subset, creating a language model from the subset, the language model comprising a plurality of n-grams each with an n-gram probability; creating a plurality of question completion suggestions based on the language model and the question prefix; and causing presentation of the plurality of question completion suggestions to the user via a user interface.