solar day vs yesterday

solar day and yesterday both are nouns.

Word	Noun	Adjective	Verb	Adverb
solar day	Yes	No	No	No
yesterday	Yes	No	No	Yes

As nouns, yesterday is a hyponym of solar day; that is, yesterday is a word with a more specific, narrower meaning than solar day:

Other hyponyms of solar day include tomorrow, today, morrow, eve, date, day of the month, date, snow day.

solar day (noun)	yesterday (noun)
time for Earth to make a complete rotation on its axis	the recent past
	the day immediately before today

solar day (adverb)	yesterday (adverb)
	on the day preceding today
	in the recent past; only a short time ago