1. A speech recognition system, comprising: an input component configured to receive a signal indicative of speech; a lexicon including words transcribed by phones; an acoustic model modeling shared phones shared among the words in the lexicon and word-specific phones shared among a selected subset of words that would otherwise be lexically transcribed with shared phones; a language model modeling word order; and a decoder coupled to the input component, the acoustic model and the language model and configured to transcribe speech in the signal into words, the words being formed by shared phones, word-specific phones, and a combination of shared phones and word-specific phones.