# R—Reflectivity > [!note] Questa pagina non è ancora tradotta e viene visualizzata in inglese. The Mean Reflectivity index R represents the average reflectivity value of the surface, or a value for how the surface interacts with light, contributing to its visual characteristics such as gloss and brightness. Reflectivity is an absolute measurement but uses a non-standard unit (arbitrary units [arb'U]) specific to the measurement system.