This International Standard IEC 62504 is of assistance in the common understanding of terms and definitions, relevant for general lighting with LED technology. The terms included are those already available in IEC LED standards or used in manufacturers' literature. This standard provides descriptive terms (like “LED light sources”) and measurable terms when modified from IEC 60050-845 (like “colour rendering index”). NOTE Annex A gives overviews of LED package design and systems composed of LED light sources and controlgear.