the state of being asleep
"The sleeping baby stirred slightly but remained fast asleep throughout the night."
quiet and inactive restfulness
"The sleeping cat stirred not even when a loud thunderclap shook the house."
the suspension of consciousness and decrease in metabolic rate
"The hibernating bear enters a deep state of sleeping to conserve energy during the harsh winter months."
The state of being asleep, or an instance of this.
"After a long day at work, I finally sank into deep sleeping and didn't wake up until noon."
In plain English: Sleeping is the noun that refers to the state of being asleep.
"The baby finally stopped crying and settled into deep sleeping after hearing the lullaby."
Usage: Use sleeping as a noun to refer specifically to the act or period of sleep itself rather than using it as an adjective before another noun like bed or bag. This usage is common in phrases such as "a good night's sleeping" but can sound unnatural compared to simply saying "sleep."
present participle of sleep
"The sleeping cat began to stretch its paws as soon as I opened the bedroom door."
In plain English: Sleeping is when your body rests and shuts down so you can recover energy.
"The baby is sleeping soundly in the crib."
Asleep.
"The baby fell asleep on the couch and is now sleeping peacefully while I finish my book."
In plain English: Sleeping as an adjective means something is not awake or active, like a person who is resting with their eyes closed.
"The sleeping baby smiled in its sleep."
Derived from Old English slēopan, the word originally meant to rest in a state of unconsciousness with closed eyes. It is formed by adding the present participle suffix -ing to the base verb sleep.