One of my favorite features in Firefox 2 is the inline spell check feature that underlines possible spelling mistakes as I type inside a web form. The spelling checker uses a "dictionary", a list of words (hopefully spelled correctly), one per line, in a plain text file named "persdict.dat".
- Remove misspelled words from your Firefox dictionary
- Remove words from the Firefox dictionary
- Edit Firefox’s Spelling Dictionary
- Firefox 2 Spelling Dictionary Hacks; Make Firefox Inline Spell Checker More Useful
You can install a dictionary for the Thunderbird email client through Thunderbird:Help Documentation:The Options Window
Dictionaries for many different languages are available through [].
Update:Authors/Creating a Dictionary explains how to create and upload a dictionary for other people to use.
Some programs use an internal data structure called a "dictionary" (also called a "hash table"). See Mac:Accessibility/UniversalAccess, LocalStorage. Such a "dictionary" (in RAM) is created and destroyed as needed, and is completely independent of the user dictionary file.