third house vs interest group

third house and interest group both are nouns.

Word	Noun	Adjective	Verb	Adverb
third house	Yes	No	No	No
interest group	Yes	No	No	No

As nouns, interest group is a hypernym of third house; that is, interest group is a word with a broader meaning than third house:

third house: an interest group that tries to influence legislators or bureaucrats to act in their favor, typically through lobbying
interest group: (usually plural) a social group whose members control some field of activity and who have common aims

Other hypernyms of third house include interest, political entity, political unit.

third house (noun)	interest group (noun)
an interest group that tries to influence legislators or bureaucrats to act in their favor, typically through lobbying	(usually plural) a social group whose members control some field of activity and who have common aims