equinoctial circle vs equinoctial line

equinoctial circle and equinoctial line both are nouns.

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

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

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

Other synonyms of equinoctial circle include celestial equator, equinoctial.

equinoctial circle (noun)	equinoctial line (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