How do I add words to the user dictionary?

Question

If someone has a word that they commonly use, but OS X Lion keeps "correcting" to something in it's dictionary, how does the user add the word to Lion's dictionary?

Answer 1

Right click on the word and choose Spelling and Grammar from the list. Then select Show Spelling and Grammar.

You'll see the option to "learn" the word (see picture).

The database (a simple text file that contains one word per line) is located in ~/Library/Spelling/LocalDictionary. It can be opened and edited using Text Edit (or your favourite editor of choice).