narthex vs anteroom

narthex and anteroom both are nouns.

Word	Noun	Adjective	Verb	Adverb
narthex	Yes	No	No	No
anteroom	Yes	No	No	No

As nouns, anteroom is a hypernym of narthex; that is, anteroom is a word with a broader meaning than narthex:

Other hypernyms of narthex include antechamber, entrance hall, foyer, hall, lobby, vestibule.

narthex (noun)	anteroom (noun)
a vestibule leading to the nave of a church	a large entrance or reception room or area
portico at the west end of an early Christian basilica or church