IES LS-2-20 (R2023)

Lighting's language fulfills the need to describe, specify, and evaluate luminous environments. Like any language, it is based on concepts and vocabulary. The concepts result from a consideration of the nature of light, vision, and architecture. The vocabulary results from the need for clarity, specificity, and precision. Only the most important quantities and units used in lighting design and illuminating engineering that relate directly to optical radiation, light, and vision are described and defined in this document. The technical words associated with lighting equipment, photometry, lighting calculations, color, and daylighting are defined in other documents in the IES Library, and they rely on an understanding of the material presented in this document.