1. Radiant Energy: total radiation energy in Joules (J)
2. Radiant flux: Radiant energy per unit time in J/s
3. Radiant flux density: Radiant flux per unit surface area in J/(m2·s) or W/m2
4. Irradiance: Radiant flux density. It refers to fluxes to or from a flat surface in all directions in J/(m2·s)
5. Radiance: Radiant flux density per unit solid angle. It refers to fluxes to or from a surface in a specific direction in J/(m2·s·sr)
6. Spectral Radiance: Radiant flux per unit wavelength in J/(m2·s·sr·mm)
7. Albedo: Reflected radiant flux density (irradiance) divided by incoming radiant flux density (irradiance) from a flat surface in all directions unitless
8. Reflectance: Reflected radiance in one direction (in J/(m2·s ·sr) times pi (in sr) divided by incoming radiant flux density (in J/(m2·s))unitless