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.