Balloon
noun
A wind boat. This is a strange one for sure. You may assume this is like one of those giant balloons you can go ride around in, and you'd be partly right. Really, this word covers the general word balloon, though it especially has to do with the toy-style balloons (or smaller balloons). It's a little round wind ship!
ふうせん
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
空に、たくさんの風船が見えます。
You can see many balloons in the sky.
あのピエロが、風船で犬を作ってくれたんだ。
That clown made a dog out of a balloon for me.
バランスボールかと思って上に立ったら、ただの大きな風船だったんです。
I thought it was a balance ball so I stood on it and realized it was just a big balloon.