A nun is a woman who has dedicated her entire life to serving God as part of a religious community. Nuns live together in buildings called convents or monasteries, following strict spiritual rules that often include prayer, study, and helping others.

Most nuns belong to the Catholic Church, though other Christian traditions have nuns too. They take special vows, which are solemn promises to live in poverty (owning little or nothing), to remain unmarried, and to obey the rules of their religious order. Many nuns wear distinctive clothing called habits, which might include long robes and head coverings.

Throughout history, nuns have played vital roles in their communities. They've run hospitals, taught in schools, cared for orphans, and preserved knowledge by copying manuscripts before printing was invented. Some religious orders of nuns focus on quiet prayer and contemplation, while others work actively in the world as teachers, nurses, or social workers.

A male equivalent is a monk, though monks and nuns often belong to different religious orders with different traditions and rules.