A slightly formal or literary alternative to やむを得ない, used to express that a situation is inevitable or beyond one's control. Often appears in set phrases like やむを得ぬ事情.
See also: やむを得ない
I will be absent due to unavoidable circumstances.
This decision was unavoidable.
Rarely used kanji form; the kanji 止む is not commonly used for this expression.
Derived from the verb 止む (to stop) in its negative form 止まない (does not stop) combined with 得ない (cannot obtain/achieve), literally meaning 'cannot stop it'. The form やむを得ぬ is a classical negative of 得る, equivalent to modern やむを得ない.