This document discusses the design features and functions of human language. It outlines 9 key design features identified by Charles Hockett that characterize human language, including having a semantic system of discrete symbols that can be combined productively and learned through cultural transmission. The document also notes there are different functions of language, such as the informative function of passing on factual information and the phatic function of maintaining social relationships. Overall, the document provides an overview of the core properties and purposes of human language systems.