expression, noun which may take the genitive case particle 'no', adverb
as much as possible; to the best of one's ability
A somewhat formal or literary expression meaning 'to the fullest extent one can'. Often used in set phrases like 能う限りの努力 or 能う限り早く. The modern equivalent is できる限り.
See also: できる限り
能う限りの援助を惜しまない。
I will spare no effort in giving as much assistance as I can.
能う限り早くお返事いたします。
I will reply as soon as I possibly can.
Modern and more common equivalent. 能う限り is a classical variant used mainly in formal or literary contexts.
From the classical verb 能う (あたう, 'to be able') + 限り (かぎり, 'limit'). The verb 能う is the classical equivalent of modern できる.