palace vs mansion house

palace and mansion house both are nouns.

Word	Noun	Adjective	Verb	Adverb
palace	Yes	No	No	No
mansion house	Yes	No	No	No

As nouns, mansion house is a hypernym of palace; that is, mansion house is a word with a broader meaning than palace:

Other hypernyms of palace include hall, manse, mansion, residence.

palace (noun)	mansion house (noun)
official residence of an exalted person (as a sovereign)	a large and imposing house
a large and stately mansion
a large ornate exhibition hall
the governing group of a kingdom