Can (Modals)

The modal 'can' is a commonly used modal verb in English. It is used to express; ability, opportunity, a request, to grant permission, to show possibility or impossibility. It is this large amount of functions and the fact that ‘can’ is replaced by other modals when it is used to express future or past time that often lead to certain errors.

Here are some examples of 'can':

He can play the piano. Ability
We can visit my sister when we are in Brighton. Opportunity
You cannot (can't) use my car. Permission
Can I borrow your pen? Request
You can learn Japanese at that school. Possibility

Can – present – past – future

Like most modal verbs 'can' is very different in the past or future. Here is how 'can' is used in different situations.

Ability

Present I can play the piano / I can't play the violin
Past (could) I could play the piano as a child. / I couldn't play the violin as a child.                                         
Future I will be able to play the piano soon / I won't be able to play the violin.

When referring to ability during a specific event 'was able to' replaces could:
With my friend's help, we were able to clear the garage in no time at all.

Opportunity

Present I'm free now. We can go. / I'm not free now. We can't go yet.
Past (be able to) I was free so we were able to go. / I was not free so we were unable to go.
Future I'll be free then so we can go. / I won't be free then so we can't go.

Permission

Present I can stay at Danny's when he's out of town. / I can't stay at Danny's when he's out of town.
Past I was allowed to stay at Danny's when he was out of town. / I wasn't allowed to stay at Danny's when he was out of town.
Future  I can stay at Danny's when he's out of town next month. / I can't stay at Danny's when he's out of town next week.

With permission 'may' is also used although this is seen as more formal.

Request

Present Can I have a coffee? / Can't I have a coffee?

With requests the time is usually the near future. 'May' or 'could' are also possible.

Possibility

Present You can earn a lot of money in gaming. / You can't earn a lot of money as a teacher

Possibility with 'can' is normally used for generalisations. 'Could' is also possible.

Now complete the following:

• 1. Now that the shopping area has become a pedestrian zone, we _ really enjoy going there.
  
  could
  can
  
  
• 2. Scuba diving alone _ be dangerous. You have to go with someone.
  
  will be able to
  can
  
  
• 3. On the train ride to Paris I _ get a lot of work done.
  
  was able to
  could
  
  
• 4. _ you understand these instructions? I have no idea what to do.
  
  can
  could
  
  
• 5. When I was young I _ read music but I’ve forgotten it all.
  
  Can
  Could
  
  
• 6. No, that _ be right. I’d better add up the figures again.
  
  couldn’t
  can't
  
  
• 7. When we were in London we _ go on stage at the National Theatre because the stage manager was Sarah's cousin.
  
  could
  were able to
  
  
• 8. I think I _ meet you tomorrow afternoon. I don't think I'll be working.
  
  will be able to/can
  could