Luminous, like its synonyms radiant, shining, glowing, and lustrous, is generally a positive adjective, especially when it describes something that doesn't literally glow, such as a face, a performance, or a poem. Luminous signs depend on a gas such as neon, krypton, argon, xenon, or radon—and you can use luminous (DayGlo) paint to make your own signs. New technologies have now given us luminous fabrics, which are being used to produce striking or creepy effects in clothing, upholstery, and interior surfaces.