valerian
noun [ U ] biology specialized uk/vəˈlɪə.ri.ən/ us/vəˈlɪr.i.ən/
缬草（一种开白色或粉色小花的植物，其根可以入药，有镇静和催眠的作用）
a plant with small white or pink flowers and a root that is used in medicines, especially as a sedative (= drug to calm you or make you sleep)