FOREWARD
(This foreword is not part of American National Standard ANSI/IES RP-16-2010.)

One of the first undertakings of the Illuminating Engineering Society was to clarify and standardize the nomenclature in its field. The Society’s Committee on Nomenclature and Standards published a provisional set of definitions in 1910. This subsequently was revised and enlarged nine times during the following 32 years. The reports of 1922, 1925, 1932, and 1942 were approved as American Standards by the American Standards Association, and the IES was designated as sponsor for future revisions under the procedure of the Association.

The last American National Standard Nomenclature and Definitions for Illuminating Engineering (RP-16) was completed and approved by the Society and by the American National Standards Institute (ANSI) in 2005.

Since the last revisions, advances in lighting technology have given birth to new lighting terminology. Better measurement techniques have led to more international agreement in fundamental units and constants used in basic laws of physics. There is greater use of SI units today in illuminating engineering. This standard reflects the above with several new terms and definitions and with revisions in existing definitions submitted through the continuous maintenance process.

The IES Nomenclature Committee, which has been primarily responsible for this revision, acknowledges the material contributions of the technical committees of the Illuminating Engineering Society in providing suggested terms and definitions pertinent to their specialized activities.

IES NOMENCLATURE COMMITTEE
James R. Cyre, Chair
C. Bernecker*
R. E. Levin
A. L. Lewis
R. G. Mistrick
E. Rinalducci
A.W. Serres
T. C. Scott
*Advisory

INTRODUCTION
[1.0] The terms defined in this Recommended Practice are in alphabetical order within each section, in the sequence listed in the Table of Contents. Individual terms may be found by using the Index.

Throughout this document, where the terms (CIE) and Commission Internationale de l’Eclairage are used, they refer to the International Commission on Illumination.

In the context of this document, SI refers to the International System of Units (abbreviated SI from the French Le Systéme International d’Unités) — a measurement system used throughout the world and commonly referred to as the metric system. Public Law 100-418 (U.S.) designated the metric system as the preferred system of weights and measures for the United States.

SCOPE
[1.1] Illuminating engineering, strictly speaking, comprises the production, measurement and application of light, or radiant energy within the limits of the visual spectrum. Since, however, most light sources furnish radiant energy also in the adjoining infrared and ultraviolet regions, and since many lamp-type devices are used for the production of radiant energy in these regions, it is customary to include the infrared and ultraviolet within the province of the illuminating engineer.