Great ape language

Research into non-human great ape language has involved teaching gorillas, chimpanzees, and orangutans to communicate with human beings and with each other using sign language, physical tokens, and lexigrams; see Yerkish. Primatologists argue that the primates' use of these tools indicates their ability to use "language", although this is not consistent with some definitions of that term.

Apes that demonstrate understanding
A production is a stream of lexemes with semantic content. A language is grammar and a set of lexemes. A sentence (or statement) is a stream of lexemes which obeys a grammar, with a beginning and an end. Non-human animals have been recorded to have produced behaviors which are consistent with meanings accorded to human sentence productions. (That is, some animals in the following species can be said to "understand" (receive), and some can "apply" (produce) consistent, appropriate, grammatical streams of communication.) David Premack and Jacques Vauclair have cited language research for the following animals:
-Common Chimpanzees
-Gorillas
-Orangutans
-Bonobos