mess hall vs dining-room

mess hall and dining-room both are nouns.

Word	Noun	Adjective	Verb	Adverb
mess hall	Yes	No	No	No
dining-room	Yes	No	No	No

As nouns, dining-room is a hypernym of mess hall; that is, dining-room is a word with a broader meaning than mess hall:

mess hall: a (large) military dining room where service personnel eat or relax
dining-room: a room used for dining

Other hypernyms of mess hall include dining room.

mess hall (noun)	dining-room (noun)
a (large) military dining room where service personnel eat or relax	a room used for dining