Sleep is a naturally recurring state of mind and body, characterized by altered consciousness, relatively inhibited sensory activity, reduced muscle activity and inhibition of nearly all voluntary muscles during rapid eye movement (REM) sleep.
It's important that you get enough sleep!
As a verb, sleep is an irregular lexical verb, specifically an irregular weak verb - it has the 3rd person form "sleeps", the -ing form "sleeping", but an irregular preterite and past participle "slept". Sleep is an intransitive verb, so cannot take a direct object.
Note "to sleep late" means to get up late, not "to go to bed late"/"go to sleep late", as some students may think.