WK34 GET IT RIGHT (2)

Have to is used to express some obligation, compulsion or necessity in the present or future.

I have to finish the work on time.

He has to be there by 3 o’clock.

You have to wait for us at the railway station.

She will have to pay the dues.

Had to is used to talk about necessity and obligation that existed in the past. Had to is the past tense form of have to.

We had to carry our own luggage.

She had to reappear for the test.

I had to consult a doctor.

We use if to introduce a possible or unreal situation or condition. 

You can only go in if you’ve got your ticket.

If you don’t add enough wood, the fire goes out.

You can drive if you’re 17.

We use when to refer to the time of a future situation or condition that we are certain of

When I’m older, I’d love to be a dancer

When we go camping, we usually take two tents.

She gets out of breath easily when she’s jogging.

We don’t use when to introduce possible or unreal situations

If Giles comes back to the office, can you tell him I’ve gone home.

The speaker does not know whether Giles is coming back to the office. It is possible, but not definite.

When Giles comes back to the office, can you tell him I’ve gone home.

The speaker is certain that Giles is coming back to the office.