Tube
Part of speech: noun
Definition: Anything that is hollow and cylindrical in shape. An approximately cylindrical container, usually with a crimped end and a screw top, used to contain and dispense semi-liquid substances. The London Underground railway system, originally referred to the lower level lines that ran in tubular tunnels as opposed to the higher ones which ran in rectangular section tunnels. (Often the tube.) A tin can containing beer (or other beverage?) A wave which pitches forward when breaking, creating a hollow space inside. A television. Also, derisively, boob tube. British: telly
Part of speech: verb
Definition: To make or use tubes
Example sentence: The average person has one Fallopian tube.
Subway
Part of speech: noun
Definition: An underground railway, especially for mass transit of people in urban areas.A rapid transit system, regardless of the elevation of its right of way.underground walkway, tunnel for pedestrians (called pedestrian underpass in US).
Example sentence: If there's an intellectual highway, there's also an intellectual subway.