Feudalism
noun
You've learned that 主義 is "-ism." So what happens when you seal up everything you build and keep it for yourself, and make that your -ism? You get feudalism. Why? Because feudalism is a system built on the idea that power should be sealed within one group or family. Anyone outside of this sealed system is a vassal to the lord — that's feudalism for you.
This is a jukugo word that uses the on'yomi readings of the kanji. You haven't seen the ほう reading for 封 yet though, so here's a mnemonic to help you out:
Everything belonged to a feudal lord under feudalism, even your home (ほう). People didn't have private property in those days, so you could only live in a home if a feudal lord gave you permission to. I guess, in a way, that means under feudalism you were always sharing your home. With a feudal lord. Aww, how nice!
今日は歴史の授業で封建主義について学びました。
Today we learned about feudalism in history class.