ostiary vs night porter

ostiary and night porter both are nouns.

Word	Noun	Adjective	Verb	Adverb
ostiary	Yes	No	No	No
night porter	Yes	No	No	No

As nouns, night porter is a hyponym of ostiary; that is, night porter is a word with a more specific, narrower meaning than ostiary:

Other hyponyms of ostiary include commissionaire, ticket collector, ticket taker.

ostiary (noun)	night porter (noun)
someone who guards an entrance	a porter on duty during the night
the lowest of the minor Holy Orders in the unreformed Western Church but now suppressed by the Roman Catholic Church