The modal auxiliary could is used in several very different
ways. One happens when sentences with can are used in
indirect (reported) speech and the main verb is past. Another
use for could is in making polite requests (in present or
future time). A third way to use could is in showing ability
(but not permission) in the past.
Examples:
Sue was able to drive a car when she was 10 years old. ----->
Sue could drive a car when she was 10 years old.
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Bobby knew how to read before he entered school. ----->
Bobby could read before he entered school.
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Ahmed had the ability to understand conversational English
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.
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Special Notes:
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In the sentences above, the time for could is past. |
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2. |
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Could shows ability in the past, but it does not
show permission in the past. The meanings of the
sentences below 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 next day.
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The negative of could is couldn't:
Joe 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
even though he'd been in the U.S. about three months.
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