Palace of Westminster vs Houses of Parliament

Palace of Westminster and Houses of Parliament both are nouns.

Word	Noun	Adjective	Verb	Adverb
Palace of Westminster	Yes	No	No	No
Houses of Parliament	Yes	No	No	No

As nouns, Palace of Westminster and Houses of Parliament are synonyms defined as:

Palace of Westminster and Houses of Parliament: the building in which the House of Commons and the House of Lords meet

Palace of Westminster (noun)	Houses of Parliament (noun)
the building in which the House of Commons and the House of Lords meet	the building in which the House of Commons and the House of Lords meet