I personally like the keyboard prediction feature in iOS 8. However some people don't. For those people, it's easy to turn it off.
Simply go Settings->General->Keyboard and turn off the "Predictive" option. You can re-enable predictions by turning the option back on.
Alternatively, if you only occasionally want to hide the predictions, you can simply swipe down from the prediction bar.
Hope that helps.
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| Keyboard with Predictions Turned On |
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| Settings to Turn Off Keyboard Predictions |
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| Keyboard with Predictions Turned Off |
