Grammar › N1 · 10 Obligation and prohibition
〜べからざる: that must not be
N1 · 10 Obligation and prohibition
Describes something that must never be done or is not allowed, before a noun.
Dictionary form of a verb + べからざる + noun: 許すべからざる行為, 欠くべからざる存在. The set phrase 欠くべからざる means indispensable. Formal. Compare 〜まじき, which is for behavior that does not fit a role.
Examples
彼の行為は、許すべからざる裏切りだ。
His act is an unforgivable betrayal.
水は、生活に欠くべからざるものだ。
Water is something indispensable to life.