equinoctial line vs equinoctial circle

equinoctial line and equinoctial circle both are nouns.

Word	Noun	Adjective	Verb	Adverb
equinoctial line	Yes	No	No	No
equinoctial circle	Yes	No	No	No

As nouns, equinoctial line and equinoctial circle are synonyms defined as:

equinoctial line and equinoctial circle: the great circle on the celestial sphere midway between the celestial poles

Other synonyms of equinoctial line include celestial equator, equinoctial.

equinoctial line (noun)	equinoctial circle (noun)
the great circle on the celestial sphere midway between the celestial poles	the great circle on the celestial sphere midway between the celestial poles