Be supposed to is used to talk about an activity or event that is expected to happen. It expresses what is expected or intended to occur. For example, "Mike is supposed to call me tomorrow" means the speaker expects Mike to call. "We are supposed to write a composition" means the teacher expects the class to write a composition. In the past form, "was supposed to" often expresses that an expected event did not happen, such as "Alice was supposed to be home at ten, but she didn’t get in until midnight," indicating Alice did not meet the expected time of 10pm.

1. 10-11 Using Supposed To
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2. Besupposedtoisused
totalkaboutanactivity
oreventthatisexpected
tohappen.
SENTENCE EXPLANATION
Mike is supposed to
call me tomorrow.
I expect Mike to call
me tomorrow.
We are supposed to
write a composition.
The teacher expects
us to write a
composition.

3. Inthepastform,be
supposedtooften
expressestheideathat
anexpectedeventdid
nothappen.
SENTENCE EXPLANATION
Alice was supposed
to be home at ten,
but she didn’t get in
until midnight.
Somebody expected
Alice to come home
by ten, but she did
not.