TeX

ΤΕΧ or TeX (correctly IPA: /tɛx/ as in Greek, often /tɛk/ in English; written with a lowercase 'e' in imitation of the logo) is a typesetting system created by Donald Knuth. Together with the METAFONT language for font description and the Computer Modern typeface, it was designed with two main goals in mind: first, to allow anybody to produce high-quality books using a reasonable amount of effort, and, second, to provide a system that would give the exact same results on all computers, now and in the future. TeX is free software and is popular in academia, especially in the mathematics, physics, computer science, linguistics, economics, political science, and engineering communities. It has largely displaced Unix troff, the other favored formatter, in many Unix installations, which use both for different purposes.

TeX is considered by most to be the best way to typeset complex mathematical formulae. It is now also being used for many other typesetting tasks, especially in the form of LaTeX and other template packages.