Jacob's ladder vs polemonium

Jacob's ladder and polemonium both are nouns.

Word	Noun	Adjective	Verb	Adverb
Jacob's ladder	Yes	No	No	No
polemonium	Yes	No	No	No

As nouns, polemonium is a hypernym of Jacob's ladder; that is, polemonium is a word with a broader meaning than Jacob's ladder:

Jacob's ladder: pinnate-leaved European perennial having bright blue or white flowers
polemonium: any plant of the genus Polemonium; most are low-growing often foul-smelling plants of temperate to Arctic regions

Jacob's ladder (noun)	polemonium (noun)
(nautical) a hanging ladder of ropes or chains supporting wooden or metal rungs or steps	any plant of the genus Polemonium; most are low-growing often foul-smelling plants of temperate to Arctic regions
pinnate-leaved European perennial having bright blue or white flowers