Sports Day
noun
Remember how 運動 means "exercise?" When you meet with a bunch of other people to exercise it's called Sports Day! This is a day at schools in Japan where everybody does physical stuff together! It's fun and also very tiring!
うんどうかい
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
明日は運動会です。
Tomorrow is sports day.
運動会の日、雨じゃないといいんですが。
I hope it doesn't rain on the day of the athletic meet.
運動会に向けて、毎日練習しています。
We practice every day in preparation for the sports festival.