18. A non-transitory computer-readable medium storing instructions executable by one or more computers which, upon such execution, cause the one or more computers to perform operations comprising: receiving a hotword followed by a voice command; determining that the voice command satisfies one or more predetermined criteria associated with designating the voice command as a hotword, wherein a voice command that is designated as a hotword is treated as a voice input regardless of whether the voice command is preceded by another hotword; and in response to determining that the voice command satisfies one or more predetermined criteria associated with designating the voice command as a hotword, designating the voice command as a hotword.
20. The non-transitory computer-readable medium of claim 18 , wherein the operations further comprise in response to designating the voice command as a hotword, undesignating another voice command that is designated as a hotword.