bannister vs barrier

bannister and barrier both are nouns.

Word	Noun	Adjective	Verb	Adverb
bannister	Yes	No	No	No
barrier	Yes	No	No	No

As nouns, barrier is a hypernym of bannister; that is, barrier is a word with a broader meaning than bannister:

bannister: a railing at the side of a staircase or balcony to prevent people from falling
barrier: a structure or object that impedes free movement

bannister (noun)	barrier (noun)
a railing at the side of a staircase or balcony to prevent people from falling	a structure or object that impedes free movement
	any condition that makes it difficult to make progress or to achieve an objective
	anything serving to maintain separation by obstructing vision or access