17. A non-transitory computer-readable storage medium storing one or more programs, the one or more programs comprising instructions, when executed by one or more processors, cause the one or more processors to: receive, from a first user device, a first pronunciation for a first named entity; receive, from a second user device, a second pronunciation for the first named entity; store the first and second pronunciations for the first named entity in a shared pronunciation lexicon receive, from a third user device, audio data representing user speech and a context of the third user device, the user speech including the first named entity in spoken form; and perform speech-to-text conversion on the audio data to generate a textual representation of the user speech, the speech-to-text conversion comprising selecting, for comparison with the audio data, the stored first pronunciation or the stored second pronunciation for the first named entity based on the context.
17. A non-transitory computer-readable storage medium storing one or more programs, the one or more programs comprising instructions, when executed by one or more processors, cause the one or more processors to: receive, from a first user device, a first pronunciation for a first named entity; receive, from a second user device, a second pronunciation for the first named entity; store the first and second pronunciations for the first named entity in a shared pronunciation lexicon receive, from a third user device, audio data representing user speech and a context of the third user device, the user speech including the first named entity in spoken form; and perform speech-to-text conversion on the audio data to generate a textual representation of the user speech, the speech-to-text conversion comprising selecting, for comparison with the audio data, the stored first pronunciation or the stored second pronunciation for the first named entity based on the context. 23. The computer-readable storage medium of claim 17 , wherein the instructions further cause the one or more processors to: determine a relevant subset of the shared pronunciation lexicon based on the context of the third user device, wherein the speech-to-text conversion on the audio data is performed using the determined relevant subset of the shared pronunciation lexicon to generate the textual representation of the user speech.