べからず・べからざる

• Reading: べからず
• Romaji: bekarazu
• Formation: Verb dictionary form + べからず (sentence-final) / Verb dictionary form + べからざる + Noun (attributive)

Meaning

An auxiliary expression meaning 'must not' or 'should not,' used to express a strong prohibition. べからず ends a sentence as a command, while べからざる modifies a following noun to mean 'that must not be' or 'inexcusable.'

べからず is the classical negative form of べし (should, must) and functions as a firm prohibition. It survives in modern Japanese primarily in fixed signs, proverbs, rules, and literary contexts. べからざる is the attributive form used to modify nouns, as in 許すべからざる行為 (an inexcusable act). Compared to modern ～てはいけない or ～てはならない, べからず sounds archaic and authoritative. It appears on signs like 芝生に入るべからず (Keep off the grass) and in well-known proverbs like 初心忘るべからず (Never forget your beginner's spirit). Despite its classical origin, it remains recognisable to all Japanese speakers.

Examples

1. 初心忘るべからず。 Never forget your beginner's spirit.
2. 関係者以外、立ち入るべからず。 Unauthorised persons must not enter.
3. それは許すべからざる行為だと断じた。 He condemned it as an inexcusable act.

Usage Guide

Context: written, proverbs, signs

Tone: authoritative

Do Say

• 他人の努力を軽んずるべからず。
• 彼の功績は無視すべからざるものである。
• 歴史の教訓を忘るべからず。

Don't Say

• ここでタバコを吸うべからず。(Using べからず in casual everyday speech — sounds overly archaic) → ここでタバコを吸ってはいけません。
• 友達に嘘をつくべからず。(Using べからず in casual personal advice — inappropriately formal) → 友達に嘘をついてはいけないよ。

Origin & History

べからず is the classical negative form of the auxiliary verb べし, which expresses obligation or strong recommendation. べし itself derives from ancient Japanese and was one of the most important auxiliaries in classical grammar. The form べからず (must not) and its attributive variant べからざる have survived into modern Japanese in fixed expressions.

Cultural Context

Generation: All ages

Social background: Universal