TeX 

TeX, and associated programs such as LaTeX, is a system for computer typesetting, for placing text on a page. (Pronounce the name "tech".)

TeX is best known for its abilities with mathematical and scientific text and other difficult typesetting jobs; it allows ordinary users to produce output of the highest typographic quality. This is crucial for complex texts, where the ability of readers to understand the material depends on the clarity with which it is presented.