The modal auxiliary could is used
in several very different
ways. One happens when
sentences with can are used in
(reported) speech and the main verb is past. Another
for could is in making polite requests (in present or
future time). A third
way to use could is in showing ability
permission) in the past.
Sue was able to drive a car
when she was 10 years old. ----->
Sue could drive a car when she was 10 years old.
how to read before he entered school. ----->
could read before he entered school.
Ahmed had the ability to understand
after he'd been in the
U.S. about three months. ----->
Ahmed could understand conversational English after he'd
been in the U.S. about three months.
||In the sentences above, the time
for could is past.
Could shows ability
in the past, but it
show permission in
the past. The meanings of the
cannot be expressed with could.
Yes, Nadia had permission
to miss class yesterday
because it was a holy
day in her religion.
No, Billy didn't have permission
to stay up late
last night. He had school the
The negative of could is couldn't:
drive a car until he was 25 years old.
Bobby couldn't read until he entered school.
Ahmed couldn't understand conversational English
though he'd been in the U.S. about three months.