LyX
LyX (styled as LyX; pronounced [ˈlɪks]) is an open source, graphical user interface document processor based on the LaTeX typesetting system. Unlike most word processors, which follow the WYSIWYG ("what you see is what you get") paradigm, LyX has a WYSIWYM ("what you see is what you mean") approach, where what shows up on the screen roughly depicts the semantic structure of the page and is only an approximation of the document produced by TeX. Since LyX relies on the typesetting system of LaTeX without being a full-fledged LaTeX editor itself, it has the power and flexibility of LaTeX, and can handle documents including books, notes, theses, academic papers, letters, etc.