Wh-words are what, when, where, who, which, why and how.

We use clauses with a wh- word:

  • In wh-questions (see Questions and Negatives):

What are you doing?
Who ate all the pies?
Why did you do that?

  • after verbs of thinking:

know - understand - suppose - remember - forget - wonder

I know where you live.
She couldn’t remember who he was.
John wondered what was going to happen next.

NOTE: We also use clauses with if

I wonder if we’ll see Peter.
She couldn’t remember if she had posted the letter.

  •  after verbs of saying:

ask - say - admit - argue - reply - agree - mention - explain - suggest

I asked what she wanted.
He tried to explain how the accident had happened.
She wouldn’t admit what she had done.
Did he say when he would come?

tell and some other verbs of saying must always have a direct object (see clauses, sentences and phrases):

tell - remind

We tried to tell them what they should do.
She reminded me where I had left the car.

  • after some verbs of thinking and saying we use wh-words and the to-infinitive:

We didn’t know what to do.
We will ask when to set off.
Nobody told me what to do.
Can anyone suggest where to go for lunch?

NOTE: We use the to-infinitive:

-- When the subject of the to-infinitive is the same as the subject of the main verb:

He didn’t know what to do >>> He didn’t know what he should do
We will ask when to set off >>> We will ask when we should set off

-- When the subject of the to-infinitive is the same as the person spoken to:

Nobody told me what to do. >>> Nobody told me what I should do.
Can anyone suggest where to go for lunch? >>> Can anyone suggest [to us] where we should go for lunch.

  • after some nouns to say more about the noun:

Is there any reason why I should stay?.
Do you remember the day when we went to Edinburgh.
That was the town where I grew up.

We often use a wh-clause after is:

I missed my bus. That’s why I was late.
This is where I live.
That’s what I thought.
Paris – that’s where we are going for our holidays.




Hello Jessmine,

I'm afraid I'm not sure I understand this sentence or what you mean by 'infinite clauses'. Does it mean that the days when it was possible to eat in the garden are gone? If so, we don't normally use the infinitive to make a verb into a noun, so I'd recommend 'eating' instead of 'to eat'. Then, since it's really a statement about time, I'd recommend 'when' instead of 'that'. Then, if the eating in the garden was only possible in the past, then 'was' should be used instead of 'is'.

I hope this helps you.

All the best,
The LearnEnglish Team

Thank you very much for your answer!
My problem lied in to eat/eating problem. And because I overheard somewhere that you generally dont use to-inf after wh-words. But it seems the problem lies elsewhere. In noun is it?
Once again thanks for answering my confusing comment.

Hello Jessmine,

I'm afraid that we don't really understand what it is that you are trying to say with your sentence. It has multiple problems and while we could guess what you want to say and try to construct the sentence for you we have no way of knowing if those guesses are correct. We could end up misleading you in that way.

If you can tell us clearly what it is that you want to express then we can try to help you to say it and can perhaps explain why your sentence is not the right way to say it.


Best wishes,


The LearnEnglish Team

Dear Sir,

I wanted to know if we can use 'wh-clauses with the to-infinitive' as in your example sentence 'He did not know what to do' in the passive as in the following sentences:

He did not know what to be done.
He knew whom to be avoided.

Thanking you!

Hello Prap,

No, I'm afraid these sentences are not grammatically correct as they stand now. You could fix them by adding the verb 'be', however:

  • He did not know what was to be done.
  • He knew whom was to be avoided.

By the way, please post your comments only once. We check all comments before they are published, which means it can take several hours before your comments appear on our site. Thanks in advance for your cooperation with this.

All the best,
The LearnEnglish Team

Hello. I wanna learn wh reduction. For ex: i didnt know what to do. I didnt know what i did. Both are same meaning or not? Thanks!

Hello kubrasokmen,

These two sentences do not have the same meaning. 'I didn't know what to do' means that you were in a situation and you didn't know what to do next.

'I didn't know what I did' is a bit unnatural; 'what I had done' or 'what I was doing,' however, could work. If you said 'I didn't know what I had done', it would mean you didn't know (at some time in the past) or realise an action that you did before that time. This could be used to say that you made a mistake, but that you didn't realise you were making a mistake at the time you did it. If you used 'what I was doing', it would be similar, except that the action would be an action you were doing at that time in the past. Neither of these clauses could be reduced to a clause with an infinitive.

In indirect speech structures, infinitives can be used after wh-words (except 'why') to communicate the idea of obligation or possibility. In your example, 'I didn't know what to do' could be a reduced form of 'I didn't know what I should do' ('should' expresses obligation) or 'I didn't know what I wanted to do' (expressing possibility). This is quite common with verbs such as 'to know', 'to decide', 'to say', 'to understand' and others.

I hope this helps.

All the best,
The LearnEnglish Team