Member of a religous order for women, living in a convent under vows of poverty, chastity, and obedience; nuns are addressed as sister. Female monasticism is not limited to Catholic, but is most prevelant there. Orders vary in the stipulation of vows, some being permanent and others for fixed periods. Orders vary in dress, purpose, and rule, but all follow the same basic principles. Nuns are devoted to a purely contemplative life, or to a life of charity, including teaching and nursing. The head of a convent is called abbess, prioress, or mother superior.