lunula

lu·nu·la

noun \ˈlü-nyə-lə\

plural lu·nu·lae \-(ˌ)lē also -ˌlī\

Definition of LUNULA

: a crescent-shaped body part: as a : the whitish mark at the base of a fingernail—called also half-moon b : the crescentic unattached border of a semilunar valve