無駄
Common
Noun
I-adj
1
noun (common) (futsuumeishi)adjectival nouns or quasi-adjectives (keiyodoshi)
futility;waste;uselessness;pointlessness;idleness
今更後悔しても無駄だ。
It's no use regretting it now.
Other forms
徒 【むだ】 (rarely used kanji form)