A bit of free education!

The tube-metro-subway thing started to annoy me a bit, so I decided to find out what is it all about.

So, as it turns out it's like that by a StackExchange:

Each city’s metro system has a “common name” that developed historically.

• London - “The Tube”, from the tube-shaped deep level bored tunnels
• Paris - metro, full name “Métropolitain”
• New York City - subway, because the main lines have significant underground sections
• Chicago - “The L” - from el, because it is mostly elevated
• Boston - “The T” - from MBTA, the Massachusetts Bay Transportation Authority
• Washington, D.C. - metro
• San Francisco - BART, Bay Area Rapid Transit