That’s not strange; I absolutely rely on my spellchecker, and I’ve accidentally added misspelled words to the dictionary when I was working too fast and clicked “Learn” instead of “Correct.” So I know how to delete words from the dictionary.
This has to do with the system-wide spellchecker; some programs might have their own spellcheckers, but if you’re talking about Pages, Mail, TextEdit or other Apple programs that are fully OS X aware, then the OS X programs use the system-wide dictionary.
The easiest way to delete a word is to go the Apple program you were using – Pages, Mail, etc. – start the Spellchecker. And then type in the misspelled word in the suggestion box at the bottom of the Spellchecker windows and then click “Forget.” If the “Forget” button is grayed out, click in the suggestion box to make it active, then “Forget” should be clickable.
And in Pages, you can also highlight the word and right click – or Command ⌘ Click – and that will bring up a menu with options to learn for forget spelling, depending on if the word is or isn’t in the dictionary.
For a walk through on forgetting words in the Pages Help section, go to the Help menu in the menu bar while in Pages, select Pages Help, and then search for “Working with Spelling Suggestions”. That will show how to use features in Spellchecker, including getting it to forget words.
There are two other ways to work with the dictionary and misspelled: manually edit the dictionary, or use a Preference Pane called Dictionary Cleaner for OS X 10.5 or higher. It has an easy to use interface to view, add, and delete your learned spellings, with support for 12 languages.
Download it here from Two A.M. Software. (Dictionary Cleaner has been discontinued).
If you really want to, you can manually edit the spellchecking dictionary. It’s located at ~/Library/Spelling/ and is named by the language you are using, i.e. “en” for English. (The “~” means your home directory, i.e. your login name directory.) If you don’t see a dictionary file in the Spelling folder, it means that you haven’t added any words to the dictionary.
To edit a dictionary file, you’ll need a plain text editor such as BBEdit, and one that will show invisibles, as each word in the file is separated by a delimiter character, which will show up as an upside down question mark in BBEdit. Use the “Find” command to find the misspelled word, delete it, save the file, and then restart for the changes to take effect.
And remember that some programs may use their own spellchecker, such as the Mac versions of Microsoft Word, so you’ll have to look around in that different spellchecker to see how to delete a word. See How do I remove misspelled words from my Microsoft Word custom dictionary?