Пожалуйста,помогите с образование множественного числа
university - universities
thief - thieves
day - days
sky - skies
ski - skis
taxi - ?
party - parties
key - keys
story - stories
way - ways
tragedy - tragedies
language - languages
leaf - leaves
comedy - comedies
knife - knives
university - universities
thief - thieves
day - days
sky - skies
ski - skis
taxi - ?
party - parties
key - keys
story - stories
way - ways
tragedy - tragedies
language - languages
leaf - leaves
comedy - comedies
knife - knives