dead end vs cul de sac

dead end and cul de sac both are nouns.

Word	Noun	Adjective	Verb	Adverb
dead end	Yes	No	No	No
cul de sac	Yes	No	No	No

As nouns, dead end and cul de sac are synonyms defined as:

Other synonyms of dead end include cul.

dead end (noun)	cul de sac (noun)
a passage with access only at one end	a street with only one way in or out
a situation in which no progress can be made or no advancement is possible	a passage with access only at one end