vagonaro

A train in Esperanto is literally a collection of carriages: vagono plus the suffix -ar-, which gathers things into a set. The same machine builds arbaro from arbo and vortaro from vorto, so once you have met one you can read the rest without a dictionary. Newer texts sometimes prefer the borrowed trajno, but vagonaro is the classic form and is what you will meet in older literature and in the Fundamento-flavoured registers. You ride one per vagonaro, using the instrumental per, and you go en la vagonaron with the accusative when you are climbing aboard rather than already sitting inside.