Помогите плизGive the plural of these nouns: university, sky, party, way, leaf, thief, ski ,key ,tragedy ,comedy, day ,taxi ,story…

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.