Traditionally this directory contains only the English words file, which is used by look(1) and various spelling programs. words may use either American or British spelling. Sites that require both may link words to /usr/share/dict/american-english or /usr/share/dict/british-english.
Word lists for other languages may be added using the English name for that language, e.g., /usr/share/dict/french, /usr/share/dict/danish, etc. These should, if possible, use an ISO 8859 character set which is appropriate for the language in question; if possible the Latin1 (ISO 8859-1) character set should be used (this is often not possible).
Other word lists, such as the web2 "dictionary" should be included here, if present.
The reason that only word lists are located here is that they are the only files common to all spell checkers.