1. For indoor luminaires, a classification system based on the percentage of flux which is emitted by the luminaire, above (or below) a horizontal plane through the center of the luminaire.
2. Floodlights: a measure of the beam spread in terms of beam angle ranges: type I, beam angle 10° to 18°; II, 18° to 29°; III, 29° to 46°; IV, 46° to 70°; V, 70° to 100°; and VI, above 100°.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.