The term INERT ELEMENT USED IN LIGHTS can be summarized as 'NEON', which is a four-letter inert element used in lights. NEON is a chemical element with the symbol Ne and atomic number 10. It is a noble gas that is colorless, odorless, and tasteless. NEON is used in a variety of applications, including lighting, signs, and lasers. It is also used in television tubes, high-voltage indicators, lightning arresters, wave meter tubes, and helium–NEON lasers.