A Catholic school teacher, perhaps, is often referred to as a NUN. A NUN is a member of a religious order of women who take vows of poverty, chastity, and obedience. They are usually associated with the Catholic Church, although some other Christian denominations also have nuns. Nuns typically wear a habit, which is a distinctive dress or garment that identifies them as members of a particular religious order. They are often involved in teaching, charity work, and other forms of service to their communities.