- Used to introduce a suggestion or proposal for a future event.
- What if we arrange it for 9:00 instead of 10:00?
- Used to introduce a speculation about a future event.
- What if we could learn to get along? What would happen then?
- Used to introduce a speculation about a past event. Often the basis for counterfactual historical interpretations.
- What if Abraham Lincoln had not been assassinated? How might the Reconstruction of the Southern States have been handled?
- (informal) A speculation as to what might have happened if something else had happened earlier.