Division
Noun and する verb
ぶんれつ
その政党は三派に分裂したと思っていたんだけど、実際は四派に分裂していたんだね。
I thought the political party was split three ways, but it was actually split four ways.
A part split is when things split into two parts. This is a split and division.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.