expressway vs state highway

expressway and state highway both are nouns.

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

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

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

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

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