1. A method for determining superwords, comprising the steps of: generating a set of candidate phrases from a database of observed sequences of words, symbols and/or sounds, the database having a perplexity value based on a language model; incorporating one of the candidate phrases from the database into the language model; analyzing how the perplexity value of the database, which is based on the language model, is affected by the incorporated candidate phrase; and determining if the candidate phrase is a superword based on the analyzing step.