Thousand Yen Bill, Thousand Yen Note
noun
You know what 千円 is (1000 yen). So if you add a bill to that you get a thousand yen bill. That's just the little rectangular piece of money that is worth 1000 yen.
せんえんさつ
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.
千円札のおつりが不足しています。
We don't have enough thousand yen bills for change.
千円札で宝くじを三口買いました。
I bought three lottery tickets with a thousand yen bill.
このUFOキャッチャーは千円札が使えません。
This crane game doesn't accept thousand yen bills.