地下鐵的英文怎麼說？

地下鐵的英文怎麼說？
The MRT? The subway? The underground? Metro?

大眾捷運系統：
MRT: massive rapid transportation
地下鐵：
(美) subway, underground line, tube 
(英) underground railway 
metro (for systems in other European countries)
(the Metro) (especially the one in Paris)

臺灣高鐵：
The Taiwan High Speed Rail (the THSR)

For more railroad English, please check
http://ms.ly.ks.edu.tw/~atlantia/learn-more/traffic/train.htm.