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.