There is a difference, and there is not a difference.
First, we recognize that the Church’s laws on religious life can be a bit complicated, because of the huge number of different religious institutes in existence founded at various times over 2,000 years of Church history.
A Catholic nun is a woman who lives a contemplative life in a monastery, which is usually cloistered (or enclosed) or semi-cloistered. Her ministry is centered on her unique prayer life within the monastery for the good of the world. She professes the perpetual solemn vows, living a life according to the evangelical counsels of poverty, celibacy and obedience.
A Catholic sister is a woman who lives, ministers and prays within the world. A sister’s life is called “active” or “apostolic” because she is engaged in the works of mercy and other ministries that take the Gospel to others where they are. She professes the same perpetual simple vows.
“Vita Consacrata,” St. John Paul II’s apostolic exhortation, states, “Consecrated life is not something isolated and marginal, but a reality which affects the whole Church. The consecrated life is at the very heart of the Church as a decisive element for her mission since it ‘manifests the inner nature of the Christian calling’ and the striving of the whole Church as Bride towards union with her one Spouse.”
In U.S. modern-day culture, it is customary to call all religious by the title of “sister.” Of course, if we see them, they are most likely religious of apostolic life. It is important to honor and respect their life – offered completely, body and soul to Lord, the Church and humanity.
By Sister Gianna Grace, Servants of the Pierced Hearts of Jesus and Mary, August 25, 2022