A sister in church can refer to a nun or a female member of a religious order who has taken vows of poverty, chastity, and obedience. In some Christian denominations, "sister" may also refer to a laywoman who has taken religious vows or a woman who is a member of a religious community. In both cases, sisters may live in convents or communities and engage in various works of service, such as teaching, nursing, and social outreach.