lexigram - a symbol representing a word/lexeme - used by chimpanzees and baboons
human language is unique because it is:
recursive - used to describe a language with units (such as sentences or phrases) that can contain themselves (such as sentences within sentences or phrases within phrases).
generative - used to describe a language that can convey an infinite number of ideas based on different combinations of words or symbols.
displacement - the ability of a language to describe things that are not present