spring equinox vs equinox

spring equinox and equinox both are nouns.

Word	Noun	Adjective	Verb	Adverb
spring equinox	Yes	No	No	No
equinox	Yes	No	No	No

As nouns, equinox is a hypernym of spring equinox; that is, equinox is a word with a broader meaning than spring equinox:

spring equinox: March 21
equinox: either of two times of the year when the sun crosses the plane of the earth's equator and day and night are of equal length

spring equinox (noun)	equinox (noun)
March 21	(astronomy) either of the two celestial points at which the celestial equator intersects the ecliptic
	either of two times of the year when the sun crosses the plane of the earth's equator and day and night are of equal length