Conditionals: Zero, First, Second, Third

Introduction

Conditional sentences express "if...then" situations. English has four main types of conditionals, each used for different levels of possibility and time.

Zero Conditional

Used for facts, general truths, and things that are always true.

Structure

If + present simple, present simple

Examples

• If you heat water to 100°C, it boils.

• If it rains, the ground gets wet.

• If you mix red and blue, you get purple.

:::tip

Zero conditional expresses cause and effect that is always true. You can replace "if" with "when" without changing the meaning.

:::

First Conditional

Used for real and possible future situations.

Structure

If + present simple, will + base verb

Examples

• If it rains tomorrow, I will stay at home.

• If you study hard, you will pass the exam.

• If she doesn't hurry, she will miss the bus.

Second Conditional

Used for unreal or unlikely present/future situations (imaginary).

Structure

If + past simple, would + base verb

Examples

• If I had a million dollars, I would travel the world.

• If she knew his number, she would call him.

• If I were you, I would accept the offer.

:::info

In formal English, use "were" instead of "was" for all subjects in the second conditional: "If I were rich..." not "If I was rich..."

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Third Conditional

Used for unreal past situations — things that did not happen, so we imagine a different result.

Structure

If + past perfect, would have + past participle

Examples

• If I had studied harder, I would have passed the exam.

• If they had left earlier, they wouldn't have missed the flight.

• If she had known about the party, she would have come.

Comparison Table

| Type | If-clause | Result clause | Use |

|------|-----------|--------------|-----|

| Zero | Present Simple | Present Simple | Facts & truths |

| First | Present Simple | Will + verb | Real future |

| Second | Past Simple | Would + verb | Unreal present/future |

| Third | Past Perfect | Would have + PP | Unreal past |

Mixed Conditionals

Sometimes we mix conditionals to talk about a past condition with a present result, or vice versa.

• Past condition, present result: If I had studied medicine (past), I would be a doctor now (present).

• Present condition, past result: If she were more careful (general trait), she wouldn't have made that mistake (past).

:::exercise

Complete the sentences with the correct conditional form:

If I ___ (be) taller, I ___ (play) basketball professionally.

If you ___ (not water) the plants, they ___ (die).

If she ___ (take) the earlier train, she ___ (arrive) on time yesterday.

If it ___ (snow) this weekend, we ___ (go) skiing.

If he ___ (know) about the meeting, he ___ (come) last night.

Answers: 1. were / would play (2nd), 2. don't water / will die (1st), 3. had taken / would have arrived (3rd), 4. snows / will go (1st), 5. had known / would have come (3rd)

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Summary

Choose your conditional based on how real or imaginary the situation is, and whether it refers to the present or past. Zero and First conditionals are for real situations; Second and Third are for imaginary ones.