The Lighting Charm (incantation: Lumos) is a charm, a light creating spell, used to illuminate the tip of the caster's wand; this light is fairly warm.
Despite its apparent simplicity, the Wand-Lighting Charm was not invented until the 18th century. It was first used publicly by Levina Monkstanley, its inventor, in the Ministry of Magic in 1772 — to the astonishment of her fellow colleagues — to help her look for a fallen quill on a dusty corner. However, Garvin Lügner, a German wizard, claimed to have been the one who invented the spell, while he was developing his Instant Darkness Powder. It later transpired that Lügner had been lying about the invention of the charm, and that his Instant Darkness Powder did not to much more than slightly dim the lights.
One of the simplest and most useful spells, it not only illuminates the wand tip, but can repel spectral foes such as Gytrashes and malevolent spirits. If one charges the spell properly, it will appear lemon-yellow; if one over-charges it, the charm will appear as a vibrant scarlet.