“The terms ‘nun’ and ‘sister’ are often used interchangeably, though technically there is a difference between the two.
Here’s a simple explanation: A nun is a woman who lives a contemplative life in a monastery which is usually cloistered, which means ‘enclosed’. Her ministry and prayer life is centred within and around the monastery for the good of the world.
A sister is a woman who lives, ministers, and prays within the world. While she often lives with other sisters, her life is called ‘active’ or ‘apostolic’ because she is engaged in the works of mercy and other ministries that take the Gospel to others.
As you can see, the difference is both in their charism (their spirituality and community lifestyle) and also their apostolate (type of work). Note that both nuns and sisters use the title ‘Sister,’ such as ‘Sister Mary Elizabeth.’
– This information was printed on an information leaflet about vocations, Archdiocese of Southwark. For more information about religious orders, links to websites of religious orders/Ecclesial Communities and consecrated life please visit http://www.ukreligiouslife.org (external link)