Apple iPhone 4G - Manual (Page 253)

Creating Dictionaries
When using certain Chinese or Japanese keyboards, you can create a dictionary
of word and input pairs. When you type a word from the dictionary while using a
supported keyboard, the associated input is substituted for the word. The dictionary is
available for the following keyboards:
Chinese - Simplified (Pinyin) Â
Chinese - Traditional (Pinyin) Â
Chinese - Traditional (Zhuyin) Â
Japanese (Romaji) Â
Japanese (Ten Key) Â
Add a word to the dictionary: In Settings, choose General > Keyboard > Edit User
Dictionary. Tap +, tap the Word field and enter the word, then tap the Yomi, Pinyin, or
Zhuyin field and enter the input.
You can have multiple inputs for each word, based on which keyboards are turned on.
Delete a word from the dictionary: Tap the word in the User Dictionary list, then tap
Delete Word.
253 Appendix A International Keyboards