secede

1. V-I If a region or group secedes from the country or larger group to which it belongs, it formally becomes a separate country or stops being a member of the larger group. (從國家或大集團中正式)脫離

Singapore seceded from the Federation of Malaysia and became an independent sovereign state. 新加坡脫離馬來西亞聯邦成爲一個獨立的主權國家。

Ukraine decided to secede. 烏尅蘭決定獨立出來。