Houses of Parliament vs Palace of Westminster

Houses of Parliament and Palace of Westminster both are nouns.

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

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

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

Houses of Parliament (noun)	Palace of Westminster (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