night shift vs graveyard shift

night shift and graveyard shift both are nouns.

Word	Noun	Adjective	Verb	Adverb
night shift	Yes	No	No	No
graveyard shift	Yes	No	No	No

As nouns, night shift and graveyard shift are synonyms defined as:

night shift and graveyard shift: workers who work during the night (as midnight to 8 a.m.)

As nouns, night shift and graveyard shift are synonyms defined as:

night shift and graveyard shift: the work shift during the night (as midnight to 8 a.m.)

night shift (noun)	graveyard shift (noun)
workers who work during the night (as midnight to 8 a.m.)	workers who work during the night (as midnight to 8 a.m.)
the work shift during the night (as midnight to 8 a.m.)	the work shift during the night (as midnight to 8 a.m.)