freeway vs state highway

freeway and state highway both are nouns.

Word	Noun	Adjective	Verb	Adverb
freeway	Yes	No	No	No
state highway	Yes	No	No	No

As nouns, freeway and state highway are synonyms defined as:

freeway and state highway: a broad highway designed for high-speed traffic

Other synonyms of freeway include expressway, motorway, pike, superhighway, throughway, thruway.

freeway (noun)	state highway (noun)
a broad highway designed for high-speed traffic	a broad highway designed for high-speed traffic