1. Can, Could, Be able to
modals

2. CAN
Possibility
Ability
BE ABLE TO
Can:
All the tenses and forms
-present
e.g. I can play chess
-future
e.g. He can’t come to the party tonight
Could:
-past
e.g. I couldn’t swim when I was 2.
-conditional
-E.g. If I could, I would help you.

3. You use CAN to
describe an ability or
speak about a possibility
in the present.
 Annie can swim, but
she can't ride a bike.
 Sorry, I can’t help you.
You can also use BE ABLE
TO to describe an ability
or speak about a possibility
in the present.
 He's able to park a
car, but he's not able
to drive in traffic yet.
 He’s crazy. He thinks
he is able to stop time
with his mind.

4. You use CAN to
describe an ability or
speak about a possibility
in the present.
 Annie can swim, but
she can't ride a bike.
 Sorry, I can’t help you.
You can also use BE ABLE
TO to describe an ability
or speak about a possibility
in the present.
 He's able to park a
car, but he's not able
to drive in traffic yet.
 He’s crazy. He thinks
he is able to stop time
with his mind.
In the PRESENT, the only difference between CAN and
BE ABLE TO, is that CAN is more common and BE
ABLE TO is more formal.

5. Use COULD to describe a
general ability or speak
about a possibility in the
past.
 My father could speak
five languages.
 He couldn’t come to
the party.
Use WAS/ WERE ABLE TO if
you are talking about what
happened in a particular situation
or speak about a possibility (this
is more formal than can) in the
past.
 Jack and John played a
tennis match yesterday
and John was able to
beat Jack.
 He wasn’t able to come
to the party.

6. But in the negatiave, you can use COULDN’T in both
cases:
 My father couldn’t
swim.
 I couldn’t read when
I was 5.
 There was a big fire
and some people
coulnd’t escape.
 Yesterday Jack
couldn’t beat John.

7. For forms and tenses other than present or past, you
have to use BE ABLE TO.
 We haven't been able to play tennis for a long
time. (Present Perfect)
 I won’t be able to be there tomorrow. (Future)
 I’ve always wanted to be able to dance. (Toinfinitive)
 She may be able to do it. (Infinitive without to
after a modal verb)
 Not being able to sleep properly changes your life
radically. (Infinitive –ing)
 etc.

8. Fill in the blanks with the correct
form of “can” or “be able to”
1. Last week I _________________(go) swimming, but this week I
can’t.
COULD GO / WAS ABLE TO GO
2. Maybe the Smiths ________________ (buy) a house next year.
WILL BE ABLE TO BUY
3. I love _________________(stay) in bed late on Sunday morning.
BEING ABLE TO STAY / TO BE ABLE TO STAY
4. I’d like ___________ (ski).
TO BE ABLE TO SKI
5. Paul _____________ (speak) French fluently.
CAN, IS ABLE TO (formal)
5. Mary _________________ (swim) since she was 3.
HAS BEEN ABLE TO SWIM