Subway

1. In American and Canadian English, a subway is a mass transit system with trains that operate underground; also known as a metro system (see also List of metro systems); also known as the underground in British English, e.g. London Underground.

2. A subway in both the UK and North America is a pedestrian tunnel that goes under a road.

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3. Subway is the trade name of a multinational franchising company selling sandwiches and salads.