noun (n)

• a bodily passage or tube lined with epithelial cells and conveying a secretion or other substance(noun.body)

  Example:
  The tear duct was obstructed.
  

  Synonym:
  canal, channel, epithelial duct
  

  source: wordnet30
• a continuous tube formed by a row of elongated cells lacking intervening end walls(noun.plant)

  source: wordnet30
• an enclosed conduit for a fluid(noun.artifact)

  source: wordnet30
• Any tube or canal by which a fluid or other substance is conducted or conveyed.(noun)

  source: webster1913