monorail vs railway system

monorail and railway system both are nouns.

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

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

monorail: a railway having a single track
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 monorail include railroad, railroad line, railway, railway line.

monorail (noun)	railway system (noun)
a railway having a single track	line that is the commercial organization responsible for operating a system of transportation for trains that pull passengers or freight