To a new word to the Windows Phone’s dictionary, write the word, tap it, and tap the plus sign (+) in the suggestion bar. Your phone also learns new words when you have written them a few times.
To correct a word, tap it, and you see suggestions for correcting the word. Your phone suggests words as you write, to help you write quickly and more accurately. Word suggestions are available in several languages. When you start writing a word, your phone suggests possible words. When the word you want is shown in the suggestion bar, select the word. To see more suggestions, swipe left.
Tip: If the suggested word is in bold, your phone automatically uses it to replace the word you wrote. If the word is wrong, tap it, and you see the original word and a few other suggestions.
Switch word suggestions off on windows phone
On the start screen, swipe left, and tap Settings > keyboard. Tap your language keyboard, and clear the Suggest text check box.