ねばなるまい

expression

ought to; should; must

A literary or formal expression equivalent to なければならない, used after the negative stem of a verb. It conveys a strong sense of obligation or necessity, often with a slightly old-fashioned or written tone.

See also: なければならない

• この問もん題だいは早そう急きゅうに解かい決けつせねばなるまい。

  We must solve this problem as soon as possible.

• 彼かれの意い見けんも聞きかねばなるまい。

  We should also listen to his opinion.