aphelion vs point of apoapsis

aphelion and point of apoapsis both are nouns.

Word	Noun	Adjective	Verb	Adverb
aphelion	Yes	No	No	No
point of apoapsis	Yes	No	No	No

As nouns, point of apoapsis is a hypernym of aphelion; that is, point of apoapsis is a word with a broader meaning than aphelion:

aphelion: apoapsis in solar orbit; the point in the orbit of a planet or comet that is at the greatest distance from the sun
point of apoapsis: (astronomy) the point in an orbit farthest from the body being orbited

Other hypernyms of aphelion include apoapsis.

aphelion (noun)	point of apoapsis (noun)
apoapsis in solar orbit; the point in the orbit of a planet or comet that is at the greatest distance from the sun	(astronomy) the point in an orbit farthest from the body being orbited