A nun's outfit is called a habit. There are many different orders of nuns, and each order wears its own variation of habit. Most traditional habits consist of the same basic pieces, though in different colours.
The first layer is usually a plain tunic. Some nuns wear a wimple on their head and neck, over the tunic. A long apronlike cloth called a scapular is worn over their shoulders. They also wear a solid veil on their head.
Different orders of nuns can be identified by their habits. Dominicans, for example, wear a traditional black and white habit, while the Missionaries of Charity wear a blue and white striped habit that resembles an Indian-style sari.
In the third century, nuns wore veils just like married women, because they believed they were brides of Christ. By the fifth century, many nuns were wearing black clothing to indicate repentance. In the Middle Ages they added the wimple, as was the appropriate fashion at the time.
Some nuns abandoned the use of traditional habits after the Council of Vatican II in the 1960s. Sometimes this was done to show that they were not in complete agreement with the teachings of the Catholic Church. Many of these orders are dying out due to dwindling numbers.
Each piece of a habit often has a short prayer that goes with it. As a nun dresses each morning, she prays the prayer associated with the article of clothing as she puts it on.