/yoo'niks/ (Or "UNIX", in the authors' words, "A weak pun on Multics") Plural "Unices". An interactive time-sharing operating system invented in 1969 by Ken Thompson after Bell Labs left the Multics project, originally so he could play games on his scavenged PDP-7. Dennis Ritchie, the inventor of C, is considered a co-author of the system.
The turning point in Unix's history came when it was reimplemented almost entirely in C during 1972 - 1974, making it the first source-portable OS. Unix subsequently underwent mutations and expansions at the hands of many different people, resulting in a uniquely flexible and developer-friendly environment.
By 1991, Unix had become the most widely used multi-user general-purpose operating system in the world. Many people consider this the most important victory yet of hackerdom over industry opposition (but see Unix weenie and Unix conspiracy for an opposing point of view).
Unix is now offered by many manufacturers and is the subject of an international standardisation effort [called?]. Unix-like operating systems include AIX, A/UX, BSD, Debian, FreeBSD, GNU, HP-UX, Linux, NetBSD, NEXTSTEP, OpenBSD, OPENSTEP, OSF, POSIX, RISCiX, Solaris, SunOS, System V, Ultrix, USG Unix, Version 7, Xenix.
"Unix" or "UNIX"? Both seem roughly equally popular, perhaps with a historical bias toward the latter. "UNIX" is a registered trademark of The Open Group, however, since it is a name and not an acronym, "Unix" has been adopted in this dictionary except where a larger name includes it in upper case. Since the OS is case-sensitive and exists in many different versions, it is fitting that its name should reflect this.