The set of all networks that can exchange electronic mail either directly or through gateways. This includes the Internet, BITNET, FidoNet, UUCP, and commercial services such as America Online, CompuServe, Delphi, and Prodigy. This term was coined by John S. Quarterman in his book The Matrix (Digital Press, 1990).
Matrix is the name of two female superheroes published by DC Comics. The original Matrix was created by John Byrne, and she first appeared (as Supergirl) in Superman vol. 2, #16 (April 1988). The current Matrix was created by Geoff Johns, Grant Morrison, Greg Rucka, Mark Waid and Dale Eaglesham and first appeared in 52 #25 (October 25 2006).