function为可数名词，意思是‘职责、功能、机能、作用’而functioning是由动词function‘尽职、起作用’转换而来的动名词，为抽象的意义，没有复数形式。双语例句
1、 He's one of the most dynamically imaginative jazz pianists still functioning.
他是当下仍旧活跃的最有闯劲、最具想象力的爵士乐钢琴师之一。
2、 The authorities say the prison is now functioning normally.
当局称监狱现在运转正常。
3、 The system was clearly not functioning smoothly or transparently.
该系统显然运行并不顺畅，也不明晰。
4、 Problems arise when the body's immune system is not functioning adequately.
免疫系统不能充分发挥作用时，身体就会出现问题.
