Et dieu créa soeur Mary

Just to add two bits to this. I, too, studied with a nun with a male saint's name, Sister Joseph Maureen. That's why I always quipped -- even before seeing Durang's play -- "The ones with the male saints' names are the worst." Sister Joseph Maureen was such a terror that I was sent to a psychologist at 7.

As to who is and isn't a "nun," for 99 percent of those in the Roman Catholic Church, both contemplative (cloistered) sisters and apostolic (out in the world as teachers, nurses and, nowadays, other occupations) sisters are referred to as "nuns." Indeed, in 1984, when I wrote my master's thesis on modern nuns, apostolic sisters freely referred to themselves and others in the apostolic orders as nuns. The distinction is not much observed in everyday speech.