means A track of parallel steel rails on which trains run, and by extension the whole system of trains, stations, and services that operate along it.

from A plain compound of "rail" and "way." "Rail" came into English from Old French "reille" (a bar or rod), itself from Latin "regula," a straight stick or rule — the same root behind "regular" and "ruler." "Way" is purely Germanic, the ancient word for a road or path. So a railway is literally a "bar-road": a way made of rules laid down in iron. The term predates steam, first used for the wooden and then iron tracks that horses dragged wagons along in mines; the locomotive arrived later and borrowed the road already named for it.