Some virches' physics differ from the ril to the extent of having more than one time dimension; others do not go to that extreme, bearing a superficial resemblance to ril physics while still allowing a 'future' event to alter a 'past' one, by various means. A particular subset of the latter, in which by one method or another at least one inhabitant of the virch is able to 'rewind' the simulation to an earlier moment and relive events from there, with knowledge of the now-erased 'future' that can be used to alter the course of events, are known as Paygeesu Virches.
The simplest version of a Paygeesu is for a virch game to have a save-point, at which the game's status at a particular game can be stored; the player can then play through from that point, and if they do not like the results, or if they just wish to try doing things a different way, can load from the save-point and try again.
Cybercosm - Text by M. Alan Kazlev Generic term for any virchworld in or apart from the Known Net; a subdivision of The Cybercosm.
Virchspace - Text by M. Alan Kazlev Any digital space or environment; pertaining to virch or a cybercosm.
Virchuniverse - Text by M. Alan Kazlev Generally, an aggregation or collection of thousands of interconnected virchworlds or cybercosms, all sharing the same basic ontology and lay-out, to make traveling from one to the other easier. Sometimes also used to designate a single extremely large virchworld.
Virchworld - Text by M. Alan Kazlev A virtual world; usually at least partially self-contained, or apparently so, may or may not include sentient beings; generally part of a cultural community across computer/cyberspace/matrix networks. The Known Net consists of literally trillions of interconnected virchworlds.