User custom dictionaries
After opening the existing user dictionary or a new one you have created, you can add words for it to ignore by clicking Add in the spell checker's Spelling window, or by typing or pasting the word directly into the Ignore this word: field in the dictionary window when you open it (see picture below). You can delete words from it in the same way as from the Ignore All ⁄ Change All dictionary.
Similarly, by clicking Auto-Correct in the spell checker's Spelling window, or by selecting the Auto-Correct Pairs tab in the user dictionary window, you can add word pairs to the Auto-Correct Pairs list. These words will automatically be replaced when encountered during a spelling check.
User dictionaries also contain an Excluded Words list which you can access by clicking the Excluded Words tab. These words will always be considered incorrect during a spell check operation. The Excluded Words list thus functions in an opposite manner to the Added Words list.