The third finger of the hand is called the digitus annularis. In Latin, the word annulus means “ring” and digitus means “finger.” The origin of the selection of the fourth finger as the ring finger is not definitively known. Before medical science discovered how the circulatory system functioned, people believed that a vein ran directly from the fourth finger on the left hand to the heart, which is why in many cultures wedding rings are worn on the ring finger of the left hand.