futile
adjective uk/ˈfjuː.taɪl/ us/ˈfjuː.t̬əl/
（行动）无作用的；无效的；不成功的
(of actions) having no effect or achieving nothing
Attempts to get supplies to the region are futile because troops will not allow the aid convoy to enter the city. 往该地区运送物资的努力失败了，因为军方不允许救援物资护送队进城。
It's completely futile trying to reason with him - he just won't listen. 跟他讲道理一点用都没有——他就是不听。
All my attempts to cheer her up proved futile. 我想让她快活起来，但所有的努力都白费了。