Lumos

Pronunciation: LOO-moss /luˈmɒs/
Description: Creates a narrow beam of light that shines from the wand's tip, like a torch. Remus Lupin also uses it in Harry Potter and the Order of the Phoenix to project a small flame (large enough to burn a piece of paper).
Etymology: Latin lumen, "light".
Notes: The movies include different variations of the spell, "Lumos Solem" and "Lumos Maxima". In the Prisoner of Azkaban movie, Professor Snape's application of Lumos created a sphere of light, rather than a beam. The counter-spell is Nox. It also seems to be undetectable by the Ministry of Magic, or else ignored, as Harry Potter uses it in Prisoner of Azkaban, Goblet of Fire and Order of the Phoenix, while outside school, without consequence.