throughway vs state highway

throughway and state highway both are nouns.

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

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

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

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

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