This document provides definitions and discussions of language, communication, and linguistics. It begins by defining language as the human system of communication using symbols like sounds, gestures, or writing. Communication is defined as the exchange of information and ideas between a sender and receiver. Linguistics is defined as the scientific study of language, including its structure, acquisition, and use. The document then discusses the origins of human language and provides examples of verbal and nonverbal communication. It describes common communication models like the Johari window and Schramm's model, which illustrate the encoding and decoding of messages between parties.