The lunula, or lunulae (pl.) (little moon in Latin), is the crescent-shaped whitish area of the bed of a fingernail or toenail. The lunula is the visible part of the root of the nail.In humans, it appears by week 14 of gestation, and has a primary structural role in defining the free edge of the distal nail plate (the part of the nail that grows outward).t is located at the end of the nail (that is closest to the skin of the finger), but it still lies under the nail. It is not actually white but only appears so when it is seen through the nail. Outlining the nail matrix, the lunula is a very delicate part of the nail structure.