Definition
without success; having no result.
徒劳地；无效地；枉然地
Despite his best efforts, his attempt to fix the old computer was in vain.
尽管他尽了最大努力，但他修理旧电脑的尝试还是徒劳无功。
They tried to convince her to change her mind, but it was all in vain.
他们试图说服她改变主意，但一切都是徒劳。
After hours of searching, they found their efforts to find the missing keys were in vain.
经过几个小时的搜索，他们发现寻找丢失钥匙的努力是徒劳的。