GNU Aspell is a spell checker designed to eventually replace Ispell. It
can be used as a library or as an independent spell checker.

Its main feature is that it does a much better job of coming up with
possible suggestions than just about any other spell checker available
for the English language, including Ispell and Microsoft Word. It also
has many other technical enhancements over Ispell, such as using shared
memory for dictionaries and intelligently handling personal
dictionaries when more than one Aspell process is open at once.