Use predictive text on iPhone
As you type text on the iPhone keyboard, Siri predicts your next word, suggests emoji that could take the place of your word, and makes other suggestions based on your recent activity and information from your apps (not available for all languages). In Messages, for example, when you type something like:
“I’m at” followed by a space, your current location appears as an option.
“My number is” followed by a space, your phone number appears as an option.
Accept or reject a predictive text suggestion
While typing text, you can do either of the following:
Accept a suggested word or emoji by tapping it; accept a highlighted suggestion by entering a space or punctuation.
When you tap a suggested word, a space appears after the word. If you enter a comma, period, or other punctuation, the space is deleted.
Reject the suggestions by tapping your original word (shown as the predictive text option with quotation marks).
Turn off predictive text
While editing text, touch and hold
or 
.Slide to Keyboard Settings, then turn off Predictive.
When you turn off predictive text, iPhone may still try to suggest corrections for misspelled words. To accept a correction, enter a space or punctuation, or tap return. To reject a correction, tap the “x.” If you reject the same suggestion a few times, iPhone stops suggesting it.