1. Basic structure
1.1. They consist of a MAIN CLAUSE and an IF-CLAUSE.
1.2. The IF-clause expresses the condition itself.
1.2.1. It is normally introduced by the conjunction "if"
1.2.2. Other conjunctions may be used:
1.2.2.1. as long as
1.2.2.2. provided/ providing
1.2.2.3. Unless
1.2.2.3.1. Meaning: "if not"
1.2.2.4. in case
1.2.2.4.1. not really a conditional.
1.2.3. The main clause expresses the result of the condition
1.3. Types
1.3.1. Type Zero
1.3.1.1. General or universal conditions
1.3.1.2. IF-clause: if + present simple
1.3.1.3. MAIN: present simple
1.3.2. Type One
1.3.2.1. Probable conditions
1.3.2.2. MAIN: future
1.3.3. Type Three
1.3.3.1. Conditions in the past (impossible)
1.3.3.2. IF-clause: if + past perfetc
1.3.3.3. MAIN: Conditional perfect
1.3.4. Type Two
1.3.4.1. Unreal or improbable
1.3.4.2. IF-clause: if + past simple
1.3.4.3. MAIN: conditional
1.4. IF-clause: if + present simple
2. Special constructions.
2.1. Type 2
2.1.1. They emphasize improbability.
2.1.2. IF-clause: should + inversion.
2.1.3. MAIN: conditional or imperative.