English Grammar - Pre-Intermediate

'For', 'Since' and 'Ago'.

We can use for or since with the present perfect to say how long something has happened.

I have known him since 1980.
I have known him for 22 years.

The meaning is the same. For is used to talk about a period of time, since to talk about when the action started.

ago is more often used with the past simple to say when something started.

He started his own business six months ago.
The first book was printed over 500 years ago.

So the difference between 'since' and 'ago'?

Since tells us the starting point of an action which is still continuing now. Ago tells us the starting point of an action which is finished.

I have lived in this city since 1980.
I left Denver to come here over twenty years ago.

Modal verbs are irregular auxiliary verbs (they don't have regular past and present forms, for example) that express ability, necessity, requests, advice, permission, probability and so on. They are generally used with other verbs in the infinitive:

(See the next sections for modal verbs "will" and "must/mustn't".)

I must go to the hotel tomorrow.
They can be very selfish!
We should leave now.

There are modal verbs which have different meanings and different functions.

Should / Shouldn't

This is used to give advice or to express what you expect.


You should go to the doctor if your headaches continue.
They should win the championship this year. They are the best team.

We use "shouldn't" to talk about something you are advising a person not to do.


If you want to pass your exams, you shouldn't go out tonight.
You shouldn't speak to your mother like that - show some respect!

May / Might

These are similar in meaning and are used to express possibility.


Q: Are you going to the cinema tonight?
A: I don't know. I might go or I might stay at home.

Used in questions, these two are ways of asking for something in a polite/formal way.

Might I borrow your telephone for a few moments?
May I open the window a little, please?

Can / Could

We have already seen that "can" can be used to talk about ability, with "could" used in the past:


I can see, but I can't dance.
Could you speak French from a young age?
My mum couldn't swim until she was 24!

We can also use "can" to talk about possibility, permission and make polite requests:


I can't come to the party tonight. (possibility)
You can't go in there! (permission)
Can you help me with this package? (request)
Could you lend me ten dollars? (polite request)

Note that all three of these modal verbs are followed directly by an infinitive verb without "to".

'Will' or 'Going To'

We have already discussed the use of "going to" to talk about the future. It is used to talk about plans already made and also to make predictions based on evidence we see now.

We will now talk about "will" and then see how they differ in direct comparison.

Will is a modal verb and is followed directly by an infinitive verb without "to".

I will see you tomorrow.
He'll go to the meeting tomorrow.

The main functions of "will" are:

a. to predict a future event:

The party will be at my house at eight o'clock.
The exam will finish in one hour.

b. to express a spontaneous decision:

I'll answer the phone.
You don't have bread! We'll go to the supermarket.

Note the difference between will and going to in this use. We use going to if a decision has been made before speaking, but will if the decision is made now.

John: What are you doing this weekend?
Mary: I'm going to visit Howard in Boston.
John: But Howard is in Chicago this weekend with his parents.
Mary: Oh! I didn't know that! I'll go and visit his brother Stefano then.

In this dialogue, Mary's first answer uses going to as it is a plan she made before. Her second answer uses will as she now has to make a new plan, and her plan to visit Stefano is made now, as she speaks.

c. to express a prediction based on opinion, not on fact.

Howes will win the election.
I think she'll get married next summer.

Here, expressions of opinion and belief are common:

I hope we'll see the start of the film
I wonder what will happen if I press this red button. Aaagh!!
She will probably be very late because of the traffic.
He's sure he'll get the job. He said the interview went quite well.

d. The old form of will, "shall" is often used to make offers and suggestions.

Shall we leave now? It's late.
That bag is very heavy. Shall I help you with it?

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"Have To" and "Must"

These two are very similar and both are used to talk about obligation.

Used in the positive/affirmative, these two are almost identical. They are used to say that there is an obligation, necessity for someone to do something.

Drivers in England have to drive on the left of the road.
All students must finish the exam by eleven o'clock.
All young Israelis have to do military service.

Usually, have to is used when there is an external obligation on you, must when the obligation comes from the speaker.

Note the difference:

It's late, I'm really tired, I must go now. Bye!
It's late. I'd love to stay but I have a meeting tomorrow morning. I have to go now. Bye!

Note the construction:

Subject + Have to
+ Infinitive without "TO"

NOT I must to go home before midnight.

Used in the negative, have to and must are very different.
Mustn't means there is an obligation not to do something. It's against the law, for example.

You mustn't drive over 70mph in this area.
Teachers mustn't hit their students.
If you drink more than a couple of beers, you mustn't try and drive home.

Don't have to, on the other hand, means there is no obligation for you to do something. In other words, it isn't necessary.

Rich people don't have to work.
You don't have to do part B of the test. That is for the other class.
In Britain, old people don't have to pay on the buses. It's free!

Must doesn't have a past form so you should use had to.

We missed the last bus last night so we had to catch a taxi.

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