Intermediate Grammar

Intermediate · Grammar Reference

Unit 9 — Conditionals and Relative Clauses

zero/first/second/third conditionals · might/could/should have done · relative clauses

9.1 Conditionals — overview

There are different ways of making sentences with if. It is important to understand the difference between sentences that express:

Type	Condition	Structure
Zero conditional	Always true / general facts	if + Present Simple, Present Simple
First conditional	Possible conditions	if + Present Simple, will + infinitive
Second conditional	Improbable or impossible present	if + Past Simple, would + infinitive
Third conditional	Impossible past conditions	if + Past Perfect, would have + past participle

Zero: If you heat metal, it expands.First: If I see Dave, I'll tell him to call you.Second: If I had the money, I'd buy a Mercedes.Third: If I'd known you were coming, I'd have cooked a meal.

9.2 Second conditional: improbable or impossible conditions

Form: if + Past Simple, would + verb

	Example
Positive	If I won some money, I'd go around the world.
Negative	My father would kill me if he could see me now.
Question	What would you do if you saw someone shoplifting?

Was can change to were in the condition clause.

If I/he were rich, I/he wouldn't have to work.

Use

Expresses an unreal situation and its probable result — improbable, imaginary, or different from known facts.
If I were you, I'd … is used to give advice.
Would can also express preference (especially with rather): I'd love a cup of tea. I'd rather have coffee.
Would can also express a request: Would you open the door for me?

9.3 First or second conditional?

Both conditionals refer to the present and future. The difference is about probability and possibility, not time.

First conditional

If I lose my job, I'll … (My company is doing badly — strong possibility)

Second conditional

If I lost my job, I'd … (I probably won't — I'm just imagining)

📌 Note

If there was/were a nuclear war, we'd all … (Said by a pessimist — uses second conditional because it seems impossible.)

9.4 Third conditional: impossible past conditions

Form: if + Past Perfect, would + have + past participle

If I'd (had) worked harder, I'd (would) have made more money.They'd (would) have been here hours ago if they'd (had) followed my directions.

Use

We use the third conditional to express an impossible situation in the past and its probable result. It is too late! These things can't change.

If she'd known he was cruel, she wouldn't have married him.

📌 Note

Other modal verbs are possible: I could have bought some new clothes if I had some money. If I'd really wanted, I could have been a professional footballer.

9.5 might/could have done

Might have done and could have done express possibilities in the past that didn't happen.

Thank goodness you went to hospital. You might have died.She could have married anyone she wanted.

They are found in the result clauses of third conditional sentences.

If I'd told him I had no money, he might have given me some.

Might have done and could have done can also express criticism.

You might have told me it was her birthday! She could have helped tidy the flat.

9.6 should have done

Should have done expresses advice for a past situation, but the advice is too late!

You should have apologized. He wouldn't have been so angry.You shouldn't have said she looked old. She really didn't like it.

Should have done can also express criticism.

You should have asked me before you borrowed my car.

9.7 Relative clauses

Relative clauses identify which person or thing we are talking about. They give more information about the person or thing.

Pronoun	Refers to	Example
who / that	people	The boy who lives next door has gone to the beach.
which / that	things	The book that you gave me is very good.
where	places	There is a photo of the hotel where we stayed.
whose	possession	That's the woman whose dog ran away.

When who or that is the object of the relative clause, it can be left out.

The film (that) I watched last night was very good.

Which can be used to refer to the whole previous sentence or idea.

I passed my driving test on the first attempt, which was a surprise.

📌 Note

In defining relative clauses — no comma — you can omit who/that/which when it is the object. In non-defining relative clauses — with commas — you cannot omit the pronoun and cannot use that.

9.8 Participles

Participles after a noun define and identify in the same way as relative clauses.

That woman driving the red Porsche is my aunt.The men seen outside the jeweller's were probably the thieves.