Interestingly, human language is not always used for communication with other humans and in some cases is incorporated into other languages. For example, the type of speech used to command dogs draws from human language but cannot be used by both parties for full communication. The study of languages is constantly evolving, in part because the way in which humans acquire language and even the origin of language is not fully understood. As such, it is impossible to fully define human language, as the subject is still hotly debated.