An archipelago is a cluster of islands scattered across an expanse of water. Solzhenitsyn uses the metaphor of an archipelago to explain the Gulag system in the Soviet Union, in which prison camps are scattered across the wide expanse of the country. As such, the “Gulag Archipelago” is a broad and connected yet widespread system which spans the entire country.

Black Maria is the name given to the darkened trucks and vans which the authorities used to round up members of the public.

The Bluecaps were the secret police who arrest many people in The Gulag Archipelago. The name is a reference to the blue hats worn by the police officers. These hats were inherited from the Tsar’s own secret police, though the Bluecaps practiced a graver and more constant form of violence which distinguishes them from their forebears. In Solzhenitsyn’s view, the only resemblance between the Soviet and Tsarist police is the color of the cap on their heads.