Established Practice
Custom
noun
Constant examples that you use all the time end up becoming part of an established practice. You constantly use them so it just stays that way after a while.
こうれい
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
うちの会社では、毎年恒例のクリスマス会があるんだよ。
It is an established practice at my company to have a Christmas party every year.