Lesson
Moral, Teachings
noun, verbal noun
At least way back in the day, things that teach instructions to people are things that teach a lesson, moral, or teachings. Back in the day, lots of learning was done through storytelling, and storytelling taught lessons and morals, thus, this word.
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.
いい教訓になりました。
It was a good lesson.
この教訓をムダにはしません。
I will not let this lesson be wasted.
今回の教訓を活かして、次回はもっと上手くやれるようにしたいと思います。
I hope to learn from the lessons learned this time and do better next time.