thirty-something vs thirties

thirty-something and thirties both are nouns.

Word	Noun	Adjective	Verb	Adverb
thirty-something	Yes	No	No	No
thirties	Yes	No	No	No

As nouns, thirty-something and thirties are synonyms defined as:

Other synonyms of thirty-something include mid-thirties.

thirty-something (noun)	thirties (noun)
the time of life between 30 and 40	the time of life between 30 and 40
	the decade from 1930 to 1939