べからず — Must Not (Classical)

Meaning & Usage

べからず is a classical prohibition meaning "must not," "should not," or "it is forbidden to." Rooted in classical (文語ぶんご / bungo) Japanese, it carries an authoritative, almost solemn weight that modern prohibition expressions simply do not match. You will rarely hear it in conversation. Look for it instead on formal signs, in historical documents, in literary prose, and in fixed expressions that have persisted into modern written Japanese.

The best-known real-world example is the sign 立たち入いるべからず (No Trespassing / Keep Out), posted on fences, gates, and restricted areas across Japan. Blunt and absolute, it leaves no room for negotiation. Compare it with the modern equivalent 立入禁止たちいりきんし (tachiiri kinshi), which reads as neutral and administrative. べからず is carved in stone; 立入禁止たちいりきんし is a bureaucratic label.

Grammatically, べからず traces back to the classical auxiliary verb べし (beshi), expressing obligation or suitability — roughly "must," "should," or "ought to." To form the prohibition, べし shifts to its irrealis stem べから (未然形みぜんけい / mizenkei), then takes the classical negative auxiliary ず. The result, べからず, literally means "it is not appropriate to [verb]" — but functions in practice as a strict, absolute prohibition.

べからざる is the second form worth mastering. Where べからず closes a predicate, べからざる modifies a noun directly — formed by swapping ず for its classical adnominal equivalent ざる (連体形れんたいけい). For example, 欠かくべからざる存在そんざい means "an indispensable being" — literally, "a being that must not be lacking." This expression appears regularly in formal journalism and academic prose even today.

Firmly written and formal in register, べからず sounds theatrical in casual speech — like quoting an ancient edict mid-conversation. Formal written prose, rhetorical essays, historical fiction, moral maxims, and institutional rule sets are its natural home. In those contexts, both べからず and べからざる carry real stylistic authority. For N1 preparation, recognizing both forms and understanding their grammatical roots is essential.

Think of べからず as "Thou shalt not" to てはならない's "you must not" in a formal memo. The phrasing alone signals the gravity of immutable law rather than a temporary policy. When a modern writer deliberately reaches for べからず, the register choice is itself the message.

Structure & Formation

べからず attaches to the dictionary form (終止形しゅうしけい / shuushikei) of verbs. Below is a summary of the key patterns:

Classical grammatical breakdown of べからず:

• べし — classical auxiliary meaning "must / should / is appropriate to"
• べから — the 未然形みぜんけい (irrealis stem) of べし
• ず — classical negative auxiliary (roughly equivalent to modern ない)
• べからず = "[it] must not / is not appropriate to [verb]"
• べからざる — ず changes to its 連体形れんたいけい (adnominal form) ざる, allowing it to precede and modify nouns directly

Note on する verbs: In highly classical contexts, する appears in its archaic form す, producing すべからず (e.g., 油断ゆだんすべからず — one must not be negligent). In modern formal writing, するべからず is equally acceptable and more widely understood. Both appear in N1 material; learn to recognize each.

Example Sentences

Formal Signs and Regulations

Moral Maxims and Proverbs

Formal Written Prose

べからざる — Attributive Noun-Modifying Form

Historical and Literary Contexts

Common Mistakes

Mistake 1: Using べからず in Casual Conversation

❌ ねえ、そんなこと言いうべからず！

✅ ねえ、そんなこと言いってはいけないよ！

べからず is a classical, literary prohibition and sounds extremely theatrical in everyday conversation — like quoting an ancient edict while chatting with friends. In casual speech, use てはいけない (must not — neutral) or てはだめ (must not — casual). Save べからず strictly for written formal contexts: signs, regulations, essays, and historical prose.

Mistake 2: Attaching べからず to the Wrong Verb Form

❌ 立たち入いりべからず /立たち入いってべからず ✅ 立たち入いるべからず

べからず must attach to the dictionary form (終止形しゅうしけい) of the verb — not the ます-stem (連用形れんようけい) and not the て-form. Many Japanese grammar patterns attach to the ます-stem, which makes this a common error for learners. Always check: verb in dictionary form + べからず.

Mistake 3: Forgetting to Change ず to ざる Before Nouns

❌ これは欠かくべからず条件じょうけんだ。

✅ これは欠かくべからざる条件じょうけんだ。

When べからず is used attributively — directly before a noun — it must change to べからざる. The classical negative auxiliary ず changes to its adnominal form ざる (連体形れんたいけい) when modifying nouns. This shift is a known N1 exam target. Remember: べからず ends sentences; べからざる modifies nouns.

Mistake 4: Using べからず with Adjectives or Nouns Directly

❌ 危険きけんべからず / 静しずかべからず ✅ 危険きけんを冒おかすべからず / 騒さわぐべからず

べからず attaches only to verbs in dictionary form. You cannot connect it directly to い-adjectives, な-adjectives, or nouns. To express a prohibition involving a state or quality, rephrase using an appropriate verb. "Must not be dangerous" → "must not take risks" (危険きけんを冒おかすべからず). "Must not be noisy" → "must not make noise" (騒さわぐべからず).

Cultural Notes

べからず's prevalence in Japanese culture reflects centuries of Confucian and Buddhist influence. Samurai codes of conduct (武士道ぶしどう / bushidō), temple regulations, and moral precepts were all written in classical Japanese — べからず was the natural form for expressing absolute prohibition. Encountering it on a shrine gate or temple fence today means reading a phrase whose form has likely gone unchanged for centuries.

In modern Japan, べからず on a sign carries a subtly different weight from contemporary equivalents like 禁止きんし (prohibited) or お断ことわり (not allowed). The classical phrasing implies timeless authority — these are not bureaucratic rules but near-immutable laws. Some traditional establishments and nature preserves use べからず deliberately to invoke this sense of gravity and historical continuity.

The attributive form べからざる has in many ways outlived べからず in frequency of use, embedding itself in certain fixed expressions that appear regularly in formal journalism, legal commentary, and academic writing. Phrases like 欠かくべからざる (indispensable), 許ゆるすべからざる (unforgivable), and 避さけるべからざる (unavoidable) are standard vocabulary in formal written Japanese. A reader of quality newspapers will encounter these regularly, even if the predicate form べからず itself feels archaic.

In literature, especially historical fiction (時代小説じだいしょうせつ) and period dramas (時代劇じだいげき), べからず appears naturally as part of the linguistic atmosphere. Authors use it to signal era, social class, and moral seriousness. Readers and viewers who recognize べからず pick up on these cues in ways that deepen the experience of engaging with classical or historical Japanese.

JLPT Tips

On the JLPT N1, べからず most commonly appears in reading comprehension passages set in formal, historical, or literary contexts, and in grammar structure questions where you must select the correct grammatical form from four options. You are expected to recognize the pattern and understand its meaning and grammatical origin — active production is tested less often.

Watch out for the difference between べからず (must not — prohibition) and the superficially similar classical expression すべからく〜べし (everyone ought to / must by all means), which comes from a completely different root — the kanji 須す, meaning "necessity." Because すべからく and すべからず look similar, test designers frequently place them as trap answer choices against each other. If you see すべからく followed by べし in the same sentence, the meaning is prescriptive ("everyone should"), not prohibitive.

Pay particular attention to the noun-modifying form べからざる. In grammar selection questions, you may be asked to choose between べからず and べからざる in a sentence with a following noun. The rule is absolute: べからず ends sentences; べからざる modifies nouns. Confusing these two is one of the most frequently tested errors at N1 level.

When べからず appears as an answer choice and the surrounding passage is clearly classical, historical, or formal in tone, it is almost certainly correct over modern alternatives like てはならない or ないこと. Read the register of the text first — archaic language patterns are your signal.

Memorize these べからざる fixed expressions — they recur in formal texts and are reliable exam material: 欠かくべからざる (indispensable), 許ゆるすべからざる (unforgivable), 避さけるべからざる (unavoidable), and 見逃みのがすべからざる (not to be overlooked). Learning them through reading real examples sticks better than drilling as a list.