This document discusses several key properties of human language and compares it to communication systems in animals. It notes that human language allows for references to past, present and future, has arbitrary connections between forms and meanings, and has an infinite potential number of utterances due to its productivity. It also discusses the discreteness and duality of language. The document then provides examples of bird calls and songs, primate communication using gestures, and characteristics of animal communication systems like their signals having set responses and functions, lack of creativity, and transmission without change across generations.