LaTeX

LaTeX (/ˈlɑːtɛk/ ^ⓘ LAH-tek or /ˈleɪtɛk/ LAY-tek, often stylized as LaTeX) is a software system for typesetting documents, based on TeX. LaTeX provides a high-level, descriptive markup language to utilize TeX more easily: TeX handles the document layout, while LaTeX handles the content side for document processing. Because the plain TeX formatting commands are elementary, it provides authors with ready-made commands for formatting and layout requirements such as chapter headings, footnotes, cross-references and bibliographies.

LaTeX was originally written in the early 1980s by Leslie Lamport at SRI International. The current version is LaTeX2e, first released in 1994 but incrementally updated starting in 2015. This update policy replaced earlier plans for a separate release of LaTeX3, which had been in development since 1989. LaTeX is free software and is distributed under the LaTeX Project Public License (LPPL).

Like TeX, LaTeX started as a writing tool for mathematicians and computer scientists, but even from early in its development, it has also been taken up by scholars who needed to write documents that include complex math expressions or non-Latin scripts, such as Arabic, Devanagari, and Chinese.

LaTeX was created in the early 1980s by Leslie Lamport when he was working at Stanford Research Institute (SRI). He needed to write TeX macros for his own use and thought that with a little extra effort, he could make a general package usable by others. Peter Gordon, an editor at Addison-Wesley, convinced him to write a LaTeX user's manual for publication (Lamport was initially skeptical that anyone would pay money for it); it came out in 1986 and sold hundreds of thousands of copies. Meanwhile, Lamport released versions of his LaTeX macros in 1984 and 1985. On 21 August 1989, at a TeX Users Group (TUG) meeting at Stanford, Lamport agreed to turn over maintenance and development of LaTeX to Frank Mittelbach. Mittelbach, along with Chris Rowley and Rainer Schöpf, formed the LaTeX3 team; in 1994, they released LaTeX2e, the current standard version. LaTeX3 has since been discontinued as a separate format and has become a programming layer within LaTeX2e since 2018.

LaTeX attempts to follow the design philosophy of separating presentation from content, so that authors can focus on the content of what they are writing without attending simultaneously to its visual appearance. In preparing a LaTeX document, the author specifies the logical structure using simple, familiar concepts such as chapter, section, table, figure, etc., and lets the LaTeX system handle the formatting and layout of these structures. As a result, it encourages the separation of the layout from the content – while still allowing manual typesetting adjustments whenever needed. This concept is similar to the mechanism by which many word processors allow styles to be defined globally for an entire document, or the use of Cascading Style Sheets in styling HyperText Markup Language (HTML) documents.

The LaTeX system is a markup language that handles typesetting and rendering, and can be arbitrarily extended by using the underlying macro language to develop custom macros such as new environments and commands. Such macros are often collected into packages, which could then be made available to address some specific typesetting needs such as the formatting of complex mathematical expressions or graphics (e.g., the use of the align environment provided by the amsmath package to produce aligned equations).

To create a document in LaTeX, a user first creates a file, such as document.tex, typically using a text editor. The user then gives their document.tex file as input to the TeX program (with the LaTeX macros loaded), which prompts TeX to write out a file suitable for onscreen viewing or printing. This write-format-preview cycle is one of the chief ways in which working with LaTeX differs from the What-You-See-Is-What-You-Get (WYSIWYG) style of document editing. It is similar to the code-compile-execute cycle known to computer programmers. Today, many LaTeX-aware editing programs make this cycle a simple matter through the pressing of a single key while showing the output preview on the screen beside the input window. Some online LaTeX editors even automatically refresh the preview, while other online tools provide incremental editing in-place, mixed in with the preview in a single window.

The characters 'T', 'E', and 'X' in the name come from the Greek capital letters tau, epsilon, and chi, as the name of TeX derives from the Ancient Greek: τέχνη ('skill', 'art', 'technique'); for this reason, TeX's creator Donald Knuth promotes its pronunciation as /tɛx/ (tekh) (that is, with a voiceless velar fricative as in Modern Greek, or the ch in loch). Lamport remarks that "TeX is usually pronounced tech, making lah-tech, lah-tech, and lay-tech the logical choices; but language is not always logical, so lay-tecks is also possible."