This International Standard IEC62504 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 IEC60050‑845 (like “colour rendering index”). NOTE AnnexA gives overviews of LED package design and systems composed of LED light sources and controlgear.