freeway vs throughway

freeway and throughway both are nouns.

Word	Noun	Adjective	Verb	Adverb
freeway	Yes	No	No	No
throughway	Yes	No	No	No

As nouns, freeway and throughway are synonyms defined as:

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

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