astronomical year vs tropical year

astronomical year and tropical year both are nouns.

Word	Noun	Adjective	Verb	Adverb
astronomical year	Yes	No	No	No
tropical year	Yes	No	No	No

As nouns, astronomical year and tropical year are synonyms defined as:

astronomical year and tropical year: the time for the earth to make one revolution around the sun, measured between two vernal equinoxes

Other synonyms of astronomical year include equinoctial year, solar year.

astronomical year (noun)	tropical year (noun)
the time for the earth to make one revolution around the sun, measured between two vernal equinoxes	the time for the earth to make one revolution around the sun, measured between two vernal equinoxes