canal

noun

• an artificial waterway constructed to allow the passage of boats or ships inland or to convey water for irrigation.
• a tubular duct in a plant or animal, serving to convey or contain food, liquid, or air:the ear canal
• Astronomy any of a number of linear markings formerly reported as seen by telescope on the planet Mars.

  [named canali ( 'channels') by G. V. Schiaparelli (1835–1910); the markings are now thought to have arisen from eye or lens defects]