Merosity refers to the number of component parts in a distinct whorl of a plant structure. The term is most commonly used in the context of a flower where it refers to the number of sepals in a whorl of the calyx, the number of petals in a whorl of the corolla, the number of stamens in a whorl of the androecium, or the number of carpels in a whorl of the gynoecium. The term may also be used to refer to the number of leaves in a leaf whorl.