railway system vs railroad line

railway system and railroad line both are nouns.

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

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

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

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

railway system (noun)	railroad line (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