“〜bekarazu・bekarazaru”: Must Not / Forbidden To 〜 (classical prohibition) [JLPT N1]

Content by NTJ Kuma · Nihongo to Japan editorial team · Updated July 27, 2026

A classical literary prohibition, common on signs and in maxims

「立入るべからず」 — that whiff of archaic prohibition on a signboard

On the sign at a construction fence or an old park, 「関係者以外、立入るべからず」 (unauthorized persons may not enter) — 「〜べからず・〜べからざる」 = must not ～, may not ～, a prohibition drawn from classical literary Japanese, carrying a weighty, archaic flavor, common on notices, regulations, maxims. This guide covers its two forms (sentence-final べからず／attributive べからざる), the 「すべからず」 attachment exception, and separating its setting from the colloquial 「てはいけない.」

Core: a thoroughly literary ‘prohibition, must-not'

「verb dictionary form ＋ べからず」 means “must not ～, may not ～,” the negative of the classical auxiliary 「べし」:

• 立入るべからず (no entry — a notice).
• 初心忘るるべからず (never forget your first resolve — Zeami's famous line).
• 許すべからざる行為 (an unforgivable act — べからざる attributive).

Feel: 「べし」 is classical literary “should, must,” and its negative 「べからず」 = “should not, may not, forbidden.” It keeps a heavy literary, archaic, weighty color, so it's not used in everyday speech but appears on signboards, regulations, slogans, maxims, in writing. It corresponds to “may not ～, no ～ing, must not ～, do not ～,” and that starchy archaic air is exactly its flavor.

Forms & attachment

Examples in use

• ここにゴミを捨てるべからず。(No dumping of trash here.) — a notice
• それは許すべからざる裏切りだった。(That was an unforgivable betrayal.) — べからざる attributive
• チームに欠くべからざる存在だ。(An indispensable presence on the team.)
• 「初心忘るるべからず」を座右の銘にしている。(I take “never forget your first resolve” as my motto.)
• 立入るべからずの看板が立っていた。(A “no entry” sign was standing there.)

⚠️ Where learners slip up

① It's classical literary, used only on notices／regulations／maxims／in writing, not in speech. The most important thing about 「べからず」 is its register — it's classical literary, with a heavy archaic, weighty, written color, appearing almost only on signboards, regulations, slogans, maxims, in formal writing (立入るべからず, 初心忘るるべからず). It's not used in everyday speech — you wouldn't tell a friend 「そこに座るべからず,」 which would sound like a period drama. For everyday “you may not ～,” use the colloquial 「てはいけない・てはならない・ないでください.」 Its English equivalents “may not ～, no ～ing” also lean formal. Test: to weightily write “must not ～, no ～” on a notice, regulation, maxim, in writing → べからず; for everyday speech → てはいけない.

② Attach the verb dictionary form; べからず sentence-final／べからざる attributive; 「する」 becomes 「すべからず.」 Get the attachment right. Precedes a verb dictionary form (立入る・忘る・許す). The two forms divide up: 「べからず」 goes sentence-final for prohibition (立入るべからず); 「べからざる」 is the attributive, modifying the following noun (許すべからざる行為 = unforgivable act, 欠くべからざる = indispensable). Note 「する」 especially: in literary Japanese it's often 「すべからず」 (not 「するべからず」 — though modern usage also shows 「するべからず,」 「すべからず」 is the more classically idiomatic), e.g. 油断すべからず. Mnemonic: dictionary form ＋ べからず (prohibition, final)／べからざる (un-～-able, attributive).

③ 「べからず」 (prohibition) ≠ the attributive 「べからざる,」 and don't confuse it with 「べし／べく.」 First sort out this pair's own forms — べからず is “prohibition” (ends the sentence); べからざる is “un-～-able” (attributive, always followed by a noun). 許すべからず (unforgivable — sentence-final) vs 許すべからざる罪 (an unforgivable crime — modifies 「罪」). Also, don't confuse it with the affirmative 「べし (should, must)」 — 「べし」 is “should do,” 「べからず」 is “must not do,” opposites (for the 「べし」-system's inevitability use, see 〈べくして〉). There's also 「べく」 (in order to ～, ought to ～), an inflection of 「べし」 with a different meaning. Test: sentence-final prohibition → べからず; modifying a noun “un-～-able” → べからざる; “should do” → べし (don't flip it with べからず).

🔄 Compare: べからず／てはいけない／べきではない／な

💡 Quick takeaway

「〜べからず・〜べからざる」 = must not ～／may not ～ (classical literary) — three points: ① the register is classical literary, only on notices／regulations／maxims／in writing — 立入るべからず, 初心忘るるべからず, not used in everyday speech (use てはいけない); ② attach the verb dictionary form, べからず sentence-final (prohibition)／べからざる attributive (un-～-able), with 「する」 as 「すべからず」; ③ don't flip it with the affirmative 「べし (should).」 This pattern has a real “historical, solemn” air — seeing 「〜べからず」 you know it's the weighty tone of a notice, regulation, or maxim. To write that classical gravity on a slogan, regulation, or maxim, 「べからず」 is spot-on; for everyday, return to the colloquial 「てはいけない.」 The same 「べし」-system pattern for “inevitability,” 〈べくして〉, pairs well with this.

❓ Quick FAQ

Q: Do 「立入るべからず」 and 「立入ってはいけない」 mean the same? What's the difference?

Same meaning (both “no entry”), the difference is register and setting. 「〜べからず」 = must not ～ (classical literary, weighty, archaic, written): it's a classical-literary prohibition with a heavy archaic, formal, written color, used almost only on signboards, regulations, slogans, maxims: 立入るべからず (no entry — written on a sign), 初心忘るるべからず (never forget your first resolve — a maxim). It has a “stiff, solemn” air, fitting for formal notices, but never used in everyday speech. 「〜てはいけない」 = may not ～ (colloquial, everyday): this is the modern colloquial prohibition, used in everyday speech and general explanation: ここに入ってはいけない (you may not come in here — colloquial), 走ってはいけない (you may not run). It's natural, general, un-stuffy. Difference: 「べからず」 is classical literary, for notices／regulations／maxims (weighty archaic); 「てはいけない」 is modern colloquial, for everyday (natural, general). Test: writing a notice, regulation, slogan, wanting that formal archaic air → べからず; everyday speech, general settings → てはいけない. E.g. a park sign reads 「芝生に入るべからず (keep off the grass)」; but warning a friend you'd say 「そこ、入っちゃいけないよ (you can't go in there).」 Same prohibition, one the literary of a signboard, one the colloquial of everyday — entirely different settings.

Q: How do I tell 「べからず」 from 「べからざる」?

The difference is sentence-final (prohibition) vs modifying a noun (attributive). These two are different inflections of the same negative of 「べし.」 「〜べからず」 = must not ～, may not ～ (sentence-final, prohibition): it ends the sentence, expressing “forbidden to do ～”: ここで泳ぐべからず (no swimming here — sentence-final), 初心忘るるべからず (never forget your first resolve — sentence-final). Seeing 「べからず」 at the end of a sentence, it's “must not ～.” 「〜べからざる」 = un-～-able, must-not-～ (attributive, modifying a noun): it's the attributive form, always followed by a noun, modifying it to mean “an un-～-able ○○”: 許すべからざる行為 (an unforgivable ‘act' — modifies 「行為」), 欠くべからざる存在 (an indispensable ‘presence' — modifies 「存在」). Difference: 「べからず」 ends the sentence (must not ～); 「べからざる」 is followed by a noun (an un-～-able ○○). Test: nothing after, sentence ends → べからず (prohibition); a noun follows → べからざる (un-～-able). E.g. 「他言するべからず (must not divulge — sentence-final prohibition)」 uses べからず; 「他言するべからざる秘密 (a secret that must not be divulged — modifies a noun)」 uses べからざる. One ends, one takes a noun — tell them apart by whether a noun follows. Common fixed attributives are 「欠くべからざる (indispensable)」 and 「許すべからざる (unforgivable)」 — handy to memorize.

🖊️ Practice Questions (5)

Q1. 「このエリアに___べからず。」(No entry — a classical literary-style notice)

(A) 立入る　(B) 立ち入って　(C) 入る　(D) 立ち入ろう

Q2. What does 「べからず」 mean?

(A) Should ~ (obligation)

(B) Forbidden to ~ / must not ~ (classical literary prohibition)

(C) May ~ (permission)

(D) Should be able to ~ (conjecture)

Q3. 「見逃す___問題だ。」(that must not be overlooked)

(A) べからざる　(B) べからず　(C) べき　(D) べし

Q4. 「する」のべからず形は？

(A) するべからず　(B) すべからず　(C) してべからず　(D) せべからず

Q5. What is the difference between 「べからず」 and 「てはいけない」?

(A) Exactly the same

(B) べからず is classical literary/written (notices, maxims); てはいけない is more modern and general

(C) べからず is affirmative; てはいけない is negative

(D) べからず attaches to verbs only; てはいけない to nouns only

Answer Explanations

1. (A) 立入る ── 「立入るべからず」; verb dictionary form + べからず; typical signboard wording.

2. (B) Forbidden to ~ / must not ~ (classical literary) ── The core of べからず: a classical literary prohibition, equivalent to the modern 「てはいけない」.

3. (A) べからざる ── 「見逃すべからざる問題」; べからざる is the attributive form of べからず, modifying the following noun 「問題」.

4. (B) すべからず ── The irregular form of する: す + べからず (not するべからず).

5. (B) べからず is classical literary; てはいけない is modern/general ── Core difference: べからず is a must-know N1 classical expression used in written notices and maxims; てはいけない is general modern usage.