Conditional sentences: real, unreal and past situations

1. Start with meaning

A conditional links a condition with its result. Choose the form by asking whether the situation is generally true, realistically possible, imaginary now, or impossible because it belongs to the past.

2. Four central patterns

• Zero: if + present, present — facts and routines: If water reaches 100°C, it boils.
• First: if + present, will + base verb — a real future possibility: If it rains, we will stay home.
• Second: if + past, would + base verb — an unreal or unlikely present/future: If I had more time, I would learn Korean.
• Third: if + past perfect, would have + V3 — an unreal past: If she had left earlier, she would have caught the bus.

3. Important details

Do not normally put will in the if-clause. In formal second conditional sentences, were can be used for all persons: If I were you… Unless can replace if…not but should not be followed by another negative.

4. Mixed time

A past condition may have a present result: If I had studied medicine, I would be a doctor now. The if-clause is third conditional in form; the result uses would be because it describes now.

5. Diagnostic method

Underline the time reference, decide whether the speaker sees it as real or unreal, then build each clause. This is safer than choosing a pattern from one verb alone.