Economics
Study Of Economics
You know how 経済 is economics, right? Well, add study to that and you have the study of economics, aka economics.
けいざいがく
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. It will help to know 経済 as well.
経済学のけの字も知らないので、学校に行くことにしたんです。
I don’t know the first thing about economics, so I decided to go to school.