请问，那个f开头的，表示 徒劳的，无效的单词是

futile

futile adjective
(of actions) having no effect or achieving nothing; unsuccessful:
Attempts to get supplies to the region are futile because troops will not allow the aid convoy to enter the city.
It's quite futile trying to reason with him - he just won't listen.
All my attempts to cheer her up proved futile.

failed
vain

futile

短语是bark at the moon

futile

furitless