Suppose . . .

Imagine . . .

Present Hypothetical

If I were rich, I would buy a bigger house.

If I had a bigger house, I would invite my friends over.

Past Hypothetical

If Jack had been there, he could have prevented the incident.

If I had seen that movie, I would have cried.

Formal Hypothetical

Should you have any questions, feel free to contact me.

Had I been there, I might have been able to help.