1. A computer-implemented method, comprising: obtaining, at a server system, information that identifies a level of inclusion of a particular word in queries that were received over a recent period of time; modifying, by the server system, a speech recognition model to revise occurrence data for the particular word based on the level of inclusion of the particular word in the queries that were received over the recent period of time, wherein revising occurrence data for the particular word comprises assigning weights to occurrences of the particular word in the queries that were received over the recent period of time, the assigned weights being higher for occurrences of the particular word received over the recent period of time than weights assigned to occurrences of the particular word received outside of the recent period of time and before the recent period of time; receiving, at the server system and from a mobile computing device, a verbal query; translating, by the server system and using the modified speech recognition model, the verbal query into” textual query, wherein the textual query includes the particular word; and determining whether the textual query represents a verbal search query or whether the textual query represents a verbal system command.