kabuki -- Japanese theatre dating from the 17th century
key light -- the first and usually most important light that a photographer, cinematographer, or other scene composer will use in a lighting setup. The purpose of the key light is to highlight the form and dimension of the subject.
keystone -- small rectangular pieces of quarter-inch plywood used on flats
kill -- 1) to lose the effectiveness of a line, action, or stage effect; 2) to eliminate something, such as a light
klieglight -- originally a light using an arc between two carbon electrodes, now synonymous with any bright light
knife -- a slender piece of metal attached to a platform and sticking down into a groove in the floor; helps to keep the platform moving straight