Canoness in the context of Religious sister

A religious sister (abbreviated: Sr.) in Christianity is a woman who has taken public vows in a religious order dedicated to apostolic works, as distinguished from a nun who lives a cloistered monastic life dedicated to prayer and labor, or a canoness regular, who provides a service to the world, either teaching or nursing, within the confines of the monastery. Nuns, religious sisters and canonesses all use the term "Sister" as a form of address. Religious sisters are found in various traditions of Christianity, particularly Catholicism, Evangelical Lutheranism and Anglicanism.

In the Catholic Church, religious sisters are associated with a religious institute. The HarperCollins Encyclopedia of Catholicism (1995) defines "congregations of sisters [as] institutes of women who profess the simple vows of poverty, chastity, and obedience, live a common life, and are engaged in ministering to the needs of society." As William Saunders writes: "When bound by simple vows, a woman is a sister, not a nun, and thereby called 'sister'. Nuns recite the Liturgy of the Hours or Divine Office in common [...] [and] live a contemplative, cloistered life in a monastery [...] behind the 'papal enclosure'. Nuns are permitted to leave the cloister only under special circumstances and with the proper permission."

White Ladies Priory (often Whiteladies Priory), once the Priory of St Leonard at Brewood, was an English priory of Augustinian canonesses, now in ruins, in Shropshire, in the parish of Boscobel, some eight miles (13 km) northwest of Wolverhampton, near Junction 3 of the M54 motorway. Dissolved in 1536, it became famous for its role in the escape of Charles II of England after the Battle of Worcester in 1651. The name 'White Ladies' refers to the canonesses who lived there and who wore white religious habits.