in botany, a genus of the monoecia tetrandria class. The calyx of the male consists of four leaves, and that that of the female of two valves; neither of them have any corolla; the male has a cup-shaped nectarium, and the female bears one smooth seed. The species are 18, three of them natives of Britain, viz. the pilafera, or Roman nettle; the arenas, or lesser nettle; and the dioica, or common nettle.