IPA: /ˈsʌb.weɪ/
KK: /ˈsʌbweɪ/
A type of train system that runs underground in a city, used for public transportation.
I took the subway to work this morning to avoid traffic.
Subway is formed from "sub-" (meaning under) and "way" (from Old English "weg", meaning path or road). The word "subway" refers to a path or road that is located underground.
Think of a path that goes 'under' ('sub-') the ground, which is what a subway is.