Underground
a.k.a. The Tube -
London's
underground train system, most of which runs deep beneath street level.
U.S.: subway, but just to make things interesting,
a "subway" in the U.K. - in
London,
at any rate - is a tunnel serving as a walkway under a busy street,
and nothing to do with the Underground at all. An American in
London
needs to pay attention and not follow signs that say "subway"
if what is wanted is the Underground.
"Scars can come in useful. I have one myself above my left knee that is a perfect map of the London Underground."
- Albus Dumbledore (PS1)[Hagrid] got stuck in the ticket barrier on the Underground and complained loudly that the seats were too small and the trains too slow (PS5)
"But how did you get to Diagon Alley to buy your school things last year?"
"I went on the Underground -"
- Arthur Weasley and Harry, comparing Floo powder with Muggle transport (CS4)
