as an adjective, 'asleep' describes a state of being, specifically the state of being in sleep or not awake. It can also metaphorically describe a lack of awareness or activity.
'asleep' is used to indicate that someone is sleeping or not awake. It's not typically used before a noun as a traditional adjective might be. Instead, it's most often used predicatively, following a linking verb like 'be.'
He is asleep on the couch.
I was asleep when the phone rang.
The whole town seemed asleep during the early morning hours.
'asleep' is different from 'sleeping.' While both can describe someone who is not awake, 'asleep' focuses on the state of being, while 'sleeping' focuses on the action. For example, 'He is asleep' vs. 'He is sleeping.' 'Asleep' can be used metaphorically. For instance, 'The conscience of the nation was asleep' means that the nation was unaware or indifferent to a particular issue. Avoid using 'asleep' before nouns. It's not common to say 'an asleep child.' Instead, use 'a sleeping child.'