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On Mac: "Add words to the spelling dictionary: Control-click a highlighted word, then choose Learn Spelling. The word won’t be flagged as misspelled in any document."

On iPhone: "Add a word: Tap the underlined word, then tap Learn Spelling (you may need to tap Replace first). The word is added to the dictionary used by Pages and other apps."
 
On Mac: "Add words to the spelling dictionary: Control-click a highlighted word, then choose Learn Spelling. The word won’t be flagged as misspelled in any document."

On iPhone: "Add a word: Tap the underlined word, then tap Learn Spelling (you may need to tap Replace first). The word is added to the dictionary used by Pages and other apps."
Now, if only words with friends had this sort of function :D
 
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