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Give the plural of these nouns:university, sky, party, way, leaf, thief, ski ,key ,tragedy ,comedy, day ,taxi ,story ,language,knife.

university-universities,sky-skies, party-parties, way-ways, leaf-leaves, thief-thieves,ski-skis ,key-keys ,tragedy-tragedies ,comedy-comedies,day-days ,taxi-taxis ,story-stories ,language-languages,knife-knives.