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