The light crescent~shaped "moon" at the base of the fingernails & toenails.

Literally everyone, ever. Including the writer of this definition.

The lunula is a semilunar (half-moon) white region at the base of the nail plate, and is generally found in the thumbnail of most people and in a varying degrees in other fingers.Air mixed in with keratin and cells rich in nuclei gives the lunula it's whitish color.