Oireachtas vs parliament

Oireachtas and parliament both are nouns.

Word	Noun	Adjective	Verb	Adverb
Oireachtas	Yes	No	No	No
parliament	Yes	No	No	No

As nouns, parliament is a hypernym of Oireachtas; that is, parliament is a word with a broader meaning than Oireachtas:

Oireachtas (noun)	parliament (noun)
the parliament of the Irish Republic	a card game in which you play your sevens and other cards in sequence in the same suit as the sevens; you win if you are the first to use all your cards
	a legislative assembly in certain countries