porter vs night porter

porter and night porter both are nouns.

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

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

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

porter (noun)	night porter (noun)
a very dark sweet ale brewed from roasted unmalted barley	a porter on duty during the night
a person employed to carry luggage and supplies
a railroad employee who assists passengers (especially on sleeping cars)
someone who guards an entrance

porter (verb)	night porter (verb)
carry luggage or supplies