14. An automated speech recognition system comprising: one or more data processing apparatus; and a computer-readable storage device having stored thereon instructions that, when executed by the one or more data processing apparatus, cause the one or more data processing apparatus to perform speech recognition operations comprising: receiving, by the one or more data processing apparatus of the automated speech recognition system, audio data and context data associated with the audio data, wherein the received context data indicates a current context of a device when the device captured the audio data; identifying, by the one or more data processing apparatus of the automated speech recognition system, a topic based on a comparison of the received context data with second context data indicating a previous context of a device, wherein identifying the topic includes: selecting, by the one or more data processing apparatus of the automated speech recognition system, a term based on the comparison between the received context data and the second context data; and in response to selecting the term, selecting, by the one or more data processing apparatus of the automated speech recognition system and as the identified topic, a topic that is associated with the selected term; based on identifying the topic, adjusting, by the one or more data processing apparatus of the automated speech recognition system, a language model based on the identified topic to adjust a likelihood that the language model indicates for one or more terms associated with the topic; determining, by the one or more data processing apparatus of the automated speech recognition system, a transcription of the audio data using the adjusted language model; and outputting, by the one or more data processing apparatus of the automated speech recognition system, the transcription determined using the adjusted language model, the transcription being output as a speech recognition output of the automated speech recognition system.
14. An automated speech recognition system comprising: one or more data processing apparatus; and a computer-readable storage device having stored thereon instructions that, when executed by the one or more data processing apparatus, cause the one or more data processing apparatus to perform speech recognition operations comprising: receiving, by the one or more data processing apparatus of the automated speech recognition system, audio data and context data associated with the audio data, wherein the received context data indicates a current context of a device when the device captured the audio data; identifying, by the one or more data processing apparatus of the automated speech recognition system, a topic based on a comparison of the received context data with second context data indicating a previous context of a device, wherein identifying the topic includes: selecting, by the one or more data processing apparatus of the automated speech recognition system, a term based on the comparison between the received context data and the second context data; and in response to selecting the term, selecting, by the one or more data processing apparatus of the automated speech recognition system and as the identified topic, a topic that is associated with the selected term; based on identifying the topic, adjusting, by the one or more data processing apparatus of the automated speech recognition system, a language model based on the identified topic to adjust a likelihood that the language model indicates for one or more terms associated with the topic; determining, by the one or more data processing apparatus of the automated speech recognition system, a transcription of the audio data using the adjusted language model; and outputting, by the one or more data processing apparatus of the automated speech recognition system, the transcription determined using the adjusted language model, the transcription being output as a speech recognition output of the automated speech recognition system. 15. The system of claim 14 , wherein identifying the topic based on the comparison of the received context data with second context data includes: identifying the topic based on a comparison of the received context data with second context data that indicates a context at a time at which the term was provided by a user, the term being designated as one of a plurality of words related to the topic.