passage vs promythium

passage and promythium both are nouns.

Word	Noun	Adjective	Verb	Adverb
passage	Yes	No	No	No
promythium	Yes	No	No	No

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

passage (noun)	promythium (noun)
a journey usually by ship	A section of text that comes before the story.
the passing of a law by a legislative body
the act of passing something to another person
the act of passing from one state or place to the next
a bodily reaction of changing from one place or stage to another
a way through or along which someone or something may pass
a path or channel or duct through or along which something may pass
a section of text; particularly a section of medium length
a short section of a musical composition
the motion of one object relative to another