A nun is a woman who has dedicated her life to religious service and contemplation, typically living under vows of poverty, chastity, and obedience in the enclosure of a monastery or convent. Nuns take solemn religious vows and are members of enclosed religious orders. The term "nun" is typically used for women who have taken "solemn" vows, while "sister" is used for women who have taken "simple" vows. In the Catholic tradition, there are many religious institutes of nuns and sisters, each with its own charism or special character.

Some key differences between nuns and sisters include:

• Vows: Nuns take solemn and public perpetual vows of chastity, poverty, and obedience, while sisters take perpetual simple vows living a life according to the evangelical counsels of poverty, celibacy, and obedience.

• Lifestyle: Nuns live a contemplative life in a monastery, usually cloistered or semi-cloistered, while sisters live, minister, and pray within the world, often engaged in works of mercy and other ministries that take the Gospel to others where they are.

• Enclosure: Nuns have a strict enclosure regulated by pontifical law, which prevents them from going out except in very rare cases approved by the regular superior and the bishop, and also prevents the entrance of strangers, even females, under pain of excommunication. Even admission to the grated parlor is not free, and interviews with regulars are subject to stringent rules. Sisters do not live in the papal enclosure.

Although the terms "nun" and "sister" are often used interchangeably, it is important to understand the differences between the two. Both nuns and sisters are women religious and constitute a beautiful way of serving Jesus Christ and all souls in the Church.