Animal languages are forms of communication between non-human animals that show similarities to human language. Animals communicate through a variety of signs, such as sounds and movements. Signing among animals may be considered a form of language if the inventory of signs is large enough, the signs are relatively arbitrary, and the animals seem to produce them with a degree of volition (as opposed to relatively automatic conditioned behaviors or unconditioned instincts, usually including facial expressions).
The current academic consensus is that animal communication systems lack key aspects that might define them as languages (or equivalent to human languages), one such aspect being humans' creation of new patterns of signs under varied circumstances. Humans routinely produce entirely new combinations of words. Some researchers, including the linguist Charles Hockett, argue that human language and animal communication differ so much that the underlying principles are unrelated. Accordingly, linguist Thomas A. Sebeok has proposed to not use the term "language" for animal sign systems. However, other linguists and biologists, including Marc Hauser, Noam Chomsky, and W. Tecumseh Fitch, assert that an evolutionary continuum exists between the communication methods of animal and human language.
