yesteryear vs old

yesteryear and old both are nouns.

Word	Noun	Adjective	Verb	Adverb
yesteryear	Yes	No	No	No
old	Yes	Yes	No	No

As nouns, old is a hyponym of yesteryear; that is, old is a word with a more specific, narrower meaning than yesteryear:

yesteryear (noun)	old (noun)
the time that has elapsed	past times

yesteryear (adjective)	old (adjective)
	of long duration; not new
	(used especially of persons) having lived for a relatively long time or attained a specific age
	skilled through long experience
	(used for emphasis) very familiar
	excellent
	just preceding something else in time or order
	belonging to some prior time