A Universe is a closed region of spacetime, like the one you (presumably) inhabit. Events that happen in one Universe cannot effect any other Universe by traveling normally through spacetime.
Universes are born when part of one universe collapses into a quantum bridge, severing its connection with the parent Universe. One form this quantum bridge can take is a black hole. When this division occurs, the Laws of Physics change slightly in the newly-birthed Universe. These changes accumulate over successive generations of Universes. The kinds of Universes that tend to spawn more Universes gradually become dominant in a process of Cosmological Evolution.
- A self-supported Universe like the one the reader is currently part of.
- A "pocket universe" with its own causal horizon but a clear hierarchical dependency on a Cosmolity.
Most people, when confined to a single Universe, have no need to name it. Some entities, however, are capable of Interuniversal Travel, a form of Object-Translational Travel. The Vimana, though they cannot perform such feats on their own, are the most prominent species to have access to the rare artifacts and locations through which such travel is possible. Throughout TTMA, their nomenclature of the Known Universes is most known and respected.
- Cosmolity where the Vimana (and therefore Humans) originated.