Systems, methods, and apparatuses including computer program products for generating a custom language model. In one implementation, a method is provided. The method includes receiving a collection of documents; clustering the documents into one or more clusters; generating a cluster vector for each cluster of the one or more clusters; generating a target vector associated with a target profile; comparing the target vector with each of the cluster vectors; selecting one or more of the one or more clusters based on the comparison; and generating a language model using documents from the one or more selected clusters.