dining-room suite vs dining room suite

dining-room suite and dining room suite both are nouns.

Word	Noun	Adjective	Verb	Adverb
dining-room suite	Yes	No	No	No
dining room suite	Yes	No	No	No

As nouns, dining-room suite and dining room suite are synonyms defined as:

dining-room suite and dining room suite: a suite of furniture for the dining room

Other synonyms of dining-room suite include dining-room set, dining room set.

dining-room suite (noun)	dining room suite (noun)
a suite of furniture for the dining room	a suite of furniture for the dining room