godan verb (-u), intransitive verb
be able to; be capable of
Archaic/literary verb meaning 'can do'. In modern Japanese, it survives almost exclusively in the set phrase 能う限り (as much as possible) and the negative form 能わず (cannot). The plain form is pronounced あとう (atō).
See also: 能わず (あたわず) · 能う限り
能う限りの努力はした。
I did my utmost; I did everything I possibly could.
Don't force him to do what he cannot do.