This Glossary is designed to serve persons who need to know the accepted meanings, within specific contexts, of the terminology used in reports, articles, regulations, and other materials dealing with aviation safety - with particular reference to terms specific to human factors in aviation safety. It is assumed that some users of the Glossary will be familiar with the nomenclature of aviation, but will need information on the language of human factors in engineering as they apply to aviation safety. Others (for example, engineers and psychologists) will have fairly extensive knowledge of the terminology of their own and related disciplines, but will need authoritative definitions of technical terms specific to aviation. Within the foregoing general framework, the following guidelines for the inclusion of terms to be defined have been observed: Aviation terms have been included insofar as they relate to aviation safety. The means that many terms have been included that refer to aviation rules, regulations, and procedures, and to aviation-related technologies and equipment (especially electronic instrumentation). Aviation terms unrelated to aviation safety have been omitted. No attempt has been made to include terms denoting equipment or instrumentation specific to particular aircraft. Aviation psychology and human factors terms have been included insofar as they apply to, and appear in the literature dealing with, aviation safety. Generally understood scientific and statistical terms have been omitted except as they have specialized applications to, or unique meanings in the context of, aviation safety. Terms referring to the metrics of physical parameters are included if they are specific to human factors in aviation safety. For terms that have more than one meaning in different disciplines or applications, or that are defined differently by various authorities, the various definitions are given and the applications of each are indicated.