This document describes three types of conditional sentences in English. Type I uses "if + present, will + verb" to talk about possibilities in the future or make promises/warnings. Type II uses "if + past simple, would + verb" to discuss present or future situations that are unlikely or imaginary. Type III uses "if + past perfect, would have + past participle" to talk about hypothetical past situations that never actually occurred.

1. CONDITIONAL SENTENCES
TYPE I
If + subject + present simple, + subject + will + verb (base form)
If I get the job, I'll invite you to dinner.
USES:
•Possibilities in the future: If I study hard, I'll pass my exams
•Promises and warnings: If you need me, I'll help you // If you eat all those sweets,
your teeth will rot.
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TYPE Il
If + subject + past simple, + subject + would + verb (base form)
If I were you, I would call him today
USES:
•For present and future hypothetcal situations; improbable/imaginary: If I were rich,
I could travel around the world.
TYPE Ill
If +subject+past perfect, +subject+would have + past participle
If I had won the lottery, I would have visited many different countries
USES:
•For hypothetical situations in the past; to speak about things that never
happened: If you had paid attention, you would have understood (but you
didn't pay attention)