This treatise analysis what functions light has in theater. It was inspired by Rosalinda Kraussessay Sculpture in the Expanded Field but builds mostly on the following three booksLinda Essig Lighting and the design idea (2nd ed), Nigel H. Morgan Stage lighting fortheater designers and Francis Reid The stage lighting handbook (6th ed). It discovers nineunique functions of light (performance style, dramatic style, image,illumination, 3Dspace, 3D form, selectivity, environment, atmosphere) and develops a graphical mappingof them based on a mapping by Reid. The functions performance style, dramatic style,image are superior the others. Some light functions are more closely related than othersand the different functions can easily be misunderstood.The functions performance style and dramatic style (or just style) are especially difficultto understand and map out. Environment and atmosphere are two functions that is inopposition to one another and it would be interesting to make an expansion around theseset of terms by using Krauss theories.