This International Standard establishes the terms, definitions, symbols, and abbreviations used in the field of natural gas. The terms and definitions have been reviewed and studied in order to cover all aspects of any particular term with input from other sources such as European Standards from CEN (The European Committee for Standardization), national standards, and existing definitions in the IGU Dictionary of the Gas Industry. The definitive intention of this document is to incorporate the reviewed definitions into the ISO/TC 193 source standards.