railroad line vs railway system

railroad line and railway system both are nouns.

Word	Noun	Adjective	Verb	Adverb
railroad line	Yes	No	No	No
railway system	Yes	No	No	No

As nouns, railroad line and railway system are synonyms defined as:

railroad line and railway system: line that is the commercial organization responsible for operating a system of transportation for trains that pull passengers or freight

Other synonyms of railroad line include railroad, railway, railway line.

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