cease to do　 長時間，甚至永遠停做某事。
cease doing　 短時停止做某事，以后還會接著做。

　　that department has ceased to exist forever.
　　那個部門已不復存在。
　　the girls ceased chatting for a moment when their teacher passed by.
　　姑娘們在老師走過時，停了會聊天。