retire vs hit the sack

retire and hit the sack both are verbs.

Word	Noun	Adjective	Verb	Adverb
retire	No	No	Yes	No
hit the sack	No	No	Yes	No

As verbs, retire and hit the sack are synonyms defined as:

Other synonyms of retire include bed, crawl in, go to bed, go to sleep, hit the hay, kip down, sack out, turn in.

retire (verb)	hit the sack (verb)
prepare for sleep	prepare for sleep
cause to get out
cause to be out on a fielding play
lose interest
pull back or move away or backward
dispose of (something no longer useful or needed)
break from a meeting or gathering
go into retirement; stop performing one's work or withdraw from one's position
withdraw from active participation
make (someone) retire
withdraw from circulation or from the market, as of bills, shares, and bonds