This document discusses how to express deductions, speculations, possibilities and expectations in English using modal verbs and expressions. It explains how to make positive and negative deductions in the present and past using "must", "can't", "must have" and "couldn't have". It also explains how to express possibilities in the present and past using "may", "might", "could", "may have", "might have" and "could have". Finally, it discusses using "should/ought to" and "should/ought to have" to express expectations, and adjectives like "likely" and "bound to" for speculation.

1. PRESENT DEDUCTIONS,
SPECULATIONS,
POSSIBILITIES AND
EXPECTATIONS

2. MUST:POSITIVE DEDUCTION
CAN´T: NEGATIVE DEDUCTION
O We use 'must' when
we believe that
something is true or
certain.
You must earn a lot of
money if you drive a
Porsche.
She must be important
because she has a
bodyguard.
O We use “can´t” when
we think that
something is
impossible, not true.
They can't be very happy
about working during the
night
He can´t earn much
money in his job because
he is still living with his
parents.

3. Might, may, could
O We use 'might', 'may' and 'could' to say
that something is possible.
I don't like the sound of the engine. It could
be a mechanical problem.( =maybe)
He may/might not like that shirt. I don’t think
it's his style..( =maybe)

4. Should/ought to
O We use “should” and “ought to” +
infinitive to say that we expect a
situation to happen.
O The operation went ok so if the doctor
sees my father today, he ought to go/he
should go home .

5. PAST DEDUCTIONS,
SPECULATIONS,
POSSIBILITIES AND
EXPECTATIONS

6. must have + past participle: + deduction
can´t /couldn´t have+ past participle :
- deduction
MUST HAVE+
PP
CAN´T/COULDN´T
HAVE+PP
O when we are sure
something was
true in the past
O Sue must have
arrived in Manchester
by now
O (=I´m sure she
arrived)
O When we are sure
something was
impossible or not true
in the past,:
O He can´t /couldn´t
have stolen the purse
as he was not in the
classroom (=I´m sure
he didn´t do it)

7. POSSIBILITY OF PAST
EVENTS
O We use may have/might have/ could
have+ past participle when we think
something was possible in the past.
O I didn´t see John last night at the party.
O He may have been sick. (=Maybe)
O He might have been sick.
O He could have been sick.

8. Should/ought to+have+pp
O To say that we expect a situation to
have happened in the past.
O If he sent the present to Spain for her
birthday a month ago, it should/ought to
have arrived by now.

9. ADJECTIVES FOR
SPECULATION
O Subject+BOUND TO/SURE TO
(sure,inevitable)
O He´s bound to /sure to pass the exam. His
level is very high.
O Subject+LIKELY/UNLIKELY TO (possible)
O He´s likely to pass the exam if he studies a
lot.
O IT IS LIKELY/UNLIKELY THAT+ sentence
O It is unlikely that he will pass the exam if the
doesn´t study.

10. ADVERBS
O Will definitely/ probably + verb (+
sentence)
O Justin will definitely turn down the offer.
O Definitely/probably won’t + verb (-
sentence)
O Claire probably won’t accept the job.
O WITH VERB «TO BE» after the verb in +
and before the verb in –
O He is definitely a leftwinger. She definitely
isn´t a rightwinger.