What is the difference between a dungeon and a oubliette?

Answer 1

The term oubliette is derived from the French word oublier, meaning to forget; an oubliette is a place where people are put and forgotten, which is to say, never released. Typically it is designed so that it can only be entered from the top, and otherwise has no windows or doors. It is basically a hole in which people can be put. Dungeon, on the other hand, is a more general term for any place of imprisonment and/or torture, traditionally located in the basement of a castle. It is not necessarily intended as a place from which there is no return (although that is a possibility).