If Clauses

1. Type 2

1.1. Hypothetical

1.2. Would + Past Simple

2. Type 3

2.1. Imagining a Different Past

2.2. Past Perfect + Would Have + Past Participle

3. Type 0

3.1. Scientific Facts

3.2. Present Simple+Present Simple

4. Type 1

4.1. Possible Future Events

4.2. Present Simple + Will/Won't + Verb