cog railway vs railway system

cog railway and railway system both are nouns.

Word	Noun	Adjective	Verb	Adverb
cog railway	Yes	No	No	No
railway system	Yes	No	No	No

As nouns, railway system is a hypernym of cog railway; that is, railway system is a word with a broader meaning than cog railway:

cog railway: railway for steep mountains; a cogwheel on the locomotive engages cogs on a center rail to provide traction
railway system: line that is the commercial organization responsible for operating a system of transportation for trains that pull passengers or freight

Other hypernyms of cog railway include railroad, railroad line, railway, railway line.

cog railway (noun)	railway system (noun)
railway for steep mountains; a cogwheel on the locomotive engages cogs on a center rail to provide traction	line that is the commercial organization responsible for operating a system of transportation for trains that pull passengers or freight