iPhone has dictionaries for all supported languages. The appropriate dictionary is activated automatically when you select a keyboard on iPhone. iPhone uses the active dictionary to suggest corrections or complete the word you’re typing.

You don’t need to interrupt your typing to accept the suggested word.

Suggested word

Accept or reject dictionary suggestions:

  • To reject the suggested word, finish typing the word as you want it, then tap the “x” to dismiss the suggestion before typing anything else. Each time you reject a suggestion for the same word, iPhone becomes more likely to accept your word.
  • To use the suggested word, type a space, punctuation mark, or return character.

NOTE: If you are entering Chinese or Japanese, tap one of the suggested alternatives.

Edit text:
Touch and hold to see a magnified view, then drag to position the insertion point.

Edit text

http://www.apple.com/iphone/tips/