Ispell is a fast screen-oriented spelling checker that displays
errors in the context of the original file, and suggests possible
corrections. Some of the salient features of ispell include its
multilingual support and integration with emacs. Ispell contains
direct support for files formatted using LaTeX and [nt]roff. The
integration into emacs supports additional formats, including
hypertext files.

ispell.el is an emacs/XEmacs interface to ispell.

Homepage:
https://my.eng.utah.edu/~kstevens/ispell-page.html
