Which should you use, sound asleep or soundly asleep? The expression sound asleep means completely asleep. There is an unidiomatic -ly in soundly asleep. Do not use soundly asleep to mean sound asleep. Alternatively, you can use fast asleep.
| Incorrect: |
He was soundly asleep.
|
| Correct: |
He was sound asleep.
|
| Correct: |
He was fast asleep.
|
