Unlearn Spellings on OS X

Built into Mac OS X is a configurable system-wide local dictionary which has a list of correctly spelled words that are unique to you. Potentially any application can be developed to make use of this service. Specifically a lot of the Apple apps such as Mail and TextEdit do use it.
When the system detects a misspelled word, the word in question is underlined in red. If you right click and choose “Learn Spelling”, that specific spelling of that word is added to the dictionary for future use.
Its very easy to ‘Learn’ a word by mistake. Historically to  remove a spelling, you would right click the word and choose unlearn which then removed that spelling from the dictionary.
As of Mac OS X 10.7 not all applications support the unlearn feature. For instance TextEdit does, but Mail does not.
So, if you add a spelling by mistake in Mail what can you do?
1. One option is to just switch to TextEdit, type the word and then right click it and select ‘Unlearn Spelling’.
This is fine but you will be surprised by how many custom spellings accumulate over time.
2. The second method allows you to bulk remove the incorrect spellings from the dictionary.

  • In The Finder, hold the alt key and then from the Go menu, choose Library.
  • In the Library folder locate a folder called “Spelling”. Inside this folder you will find a file called ‘LocalDictionary ‘. Double click the file to open it in TextEdit so we can edit it.
  • Remove any words  you don’t want. Then save and exit.

From experience you may have to log out and back in again, to pick up the changes.
Another use of this method is if you want to make sure certain words are in the dictionary on all your Macs. To do this just update one copy of the file ‘LocalDictionary’ with the spellings you want. Then distribute this file to all other Macs that require it.