useless, profitless, in vain, no avail ☊ 
vô ích 
useless like: vô ích → →
vergeblich ☊ 
vô ích ☊ 
无济于事的 ☊ wú jì yú shì de vergeblich ☊ vô ích ☊ ☊ It's useless for us to continue. ☊ for ☊
She tried in vain to point out to him the unfairness of his actions. ☊ point out (to sb), point sth out (to sb) ☊
search (for sth/sb): She searched in vain for her passport. ☊ search ☊
seek for sth/sb: They sought in vain for somewhere to shelter. ☊ seek ☊
The glue's useless—the pieces just won't stick. ☊ stick ☊
It would be unkind to go without him. ☊ unkind ☊
useless (to do sth): He knew it was useless to protest. ☊ useless ☊
The quality ranged from acceptable to worse than useless. ☊ useless ☊