/tekh/ An extremely powerful macro-based text formatter written by Donald Knuth, very popular in academia, especially in the computer-science community (it is good enough to have displaced Unix troff, the other favoured formatter, even at many Unix installations).
Knuth began TeX because he had become annoyed at the declining quality of the typesetting in volumes I-III of his monumental "Art of Computer Programming" (see Knuth, also bible). In a manifestation of the typical hackish urge to solve the problem at hand once and for all, he began to design his own typesetting language. He thought he would finish it on his sabbatical in 1978; he was wrong by only about 8 years. The language was finally frozen around 1985, but volume IV of "The Art of Computer Programming" has yet to appear as of mid-1997. (However, the third edition of volumes I and II have come out). The impact and influence of TeX's design has been such that nobody minds this very much. Many grand hackish projects have started as a bit of toolsmithing on the way to something else; Knuth's diversion was simply on a grander scale than most.
TeX has also been a noteworthy example of free, shared, but high-quality software. Knuth offers monetary awards to people who find and report a bug in it: for each bug the award is doubled. (This has not made Knuth poor, however, as there have been very few bugs and in any case a cheque proving that the owner found a bug in TeX is rarely cashed). Though well-written, TeX is so large (and so full of cutting edge technique) that it is said to have unearthed at least one bug in every Pascal system it has been compiled with.
TeX fans insist on the correct (guttural) pronunciation, and the correct spelling (all caps, squished together, with the E depressed below the baseline; the mixed-case "TeX" is considered an acceptable kluge on ASCII-only devices). Fans like to proliferate names from the word "TeX" - such as TeXnician (TeX user), TeXhacker (TeX programmer), TeXmaster (competent TeX programmer), TeXhax, and TeXnique.
Several document processing systems are based on TeX, notably LaTeX Lamport TeX - incorporates document styles for books, letters, slides, etc., jadeTeX uses TeX as a backend for printing from James' DSSSL Engine, and Texinfo, the GNU document processing system. Numerous extensions to TeX exist, among them BibTeX for bibliographies (distributed with LaTeX), PDFTeX modifies TeX to produce PDF and Omega extends TeX to use the Unicode character set.
See also Comprehensive TeX Archive Network.