sidereal year vs sidereal time

sidereal year and sidereal time both are nouns.

Word	Noun	Adjective	Verb	Adverb
sidereal year	Yes	No	No	No
sidereal time	Yes	No	No	No

As nouns, sidereal time is a hypernym of sidereal year; that is, sidereal time is a word with a broader meaning than sidereal year:

sidereal year: the time for the earth to make one complete revolution around the sun, relative to the fixed stars
sidereal time: measured by the diurnal motion of stars

Other hypernyms of sidereal year include year.

sidereal year (noun)	sidereal time (noun)
the time for the earth to make one complete revolution around the sun, relative to the fixed stars	measured by the diurnal motion of stars