mid-thirties vs thirties

mid-thirties and thirties both are nouns.

Word	Noun	Adjective	Verb	Adverb
mid-thirties	Yes	No	No	No
thirties	Yes	No	No	No

As nouns, mid-thirties and thirties are synonyms defined as:

Other synonyms of mid-thirties include thirty-something.

mid-thirties (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