sleep vs log Z's

sleep is a noun but log Z's is not a noun.

Word	Noun	Adjective	Verb	Adverb
sleep	Yes	No	Yes	No
log Z's	No	No	Yes	No

As verbs, sleep and log Z's are synonyms defined as:

Other synonyms of sleep include catch some Z's, kip, slumber.

sleep (noun)	log Z's (noun)
a natural and periodic state of rest during which consciousness of the world is suspended
euphemisms for death (based on an analogy between lying in a bed and in a tomb)
a torpid state resembling deep sleep
a period of time spent sleeping

sleep (verb)	log Z's (verb)
be asleep	be asleep
be able to accommodate for sleeping