freeway vs turnpike

freeway and turnpike both are nouns.

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

As nouns, turnpike is a hyponym of freeway; that is, turnpike is a word with a more specific, narrower meaning than freeway:

Other hyponyms of freeway include autobahn, autostrada, toll road.

freeway (noun)	turnpike (noun)
a broad highway designed for high-speed traffic	an expressway on which tolls are collected
	(from 16th to 19th centuries) gates set across a road to prevent passage until a toll had been paid