む / むず: Conjecture & Volition | Japanese Grammar

Modern textbooks hand you the volitional form 〜う・よう ("let's," "I'll," "shall we") as a fresh piece of grammar with no history. It has a very long history. It is the classical auxiliary む, worn down but unmistakable — 行かむ became 行こう, 見む became 見よう, and せむ became しよう. This page teaches む (and its emphatic twin むず), the single auxiliary that fuses conjecture, volition, and invitation into one form. The reward is large: once you see that 〜う・よう, colloquial 〜ん, and formal 〜んとす are all the same む at different stages of wear, a scattered set of "unrelated" endings collapses into one word you already know.

What む does: one form, several shades

む attaches to the 未然形（みぜんけい, irrealis form) and conjugates on a reduced 四段 pattern (終止む, 連体む, 已然め). Its meaning slides across a small range that all share one core — the event is not yet real, it is projected, willed, or supposed:

推量（すいりょう, conjecture) — "will probably, surely will" (typically 3rd person)
意志（いし, volition) — "I will, I shall" (1st person)
勧誘（かんゆう）・適当 — "let's, why not, you should" (2nd person)
仮定・婉曲（かてい・えんきょく, hypothetical/softening) — in the 連体形: "one who would…," "something like…"

Which shade you get is read off the subject, exactly as English "will" shifts between prediction and promise.

雨降らむ。

ame furamu

It will probably rain. (conjecture — 3rd person)

我、都へ上らむ。

ware, miyako e noboramu

I shall go up to the capital. (volition — 1st person)

いざ、共に行かむ。

iza, tomo ni ikamu

Come, let us go together. (invitation — a rallying cry)

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む is "will" in the full English sense — it covers both "it will rain" (prediction) and "I will go" (resolve). Don't hunt for one fixed translation; read the person and mood, then choose conjecture, volition, or "let's."

むず — the emphatic む

むず is simply む + と + す contracted, an emphatic/colloquial variant that carried the same meanings in Heian prose. It attaches to the 未然形 and conjugates サ変-style (終止むず, 連体むずる, 已然むずれ).

この子は、やがて大事を成さむず。

kono ko wa, yagate daiji o nasamuzu

This child will surely accomplish great things one day. (emphatic conjecture)

む → 〜う・よう: the volitional you already use

Now the descent, step by step. The 終止形む lost its consonant and its vowel fused with the stem:

Classical (む)	Middle stage	Modern volitional	Meaning
行かむ	行かう	行こう	let's go / I'll go
見む	—	見よう	let's look / I'll look
せむ	せう	しよう	let's do / I'll do
飲まむ	飲まう	飲もう	let's drink

疲れたから、そろそろ帰ろう。

tsukareta kara, sorosoro kaerō

I'm tired, so let's head home soon. (帰ろう is 帰らむ worn down)

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Every volitional you've ever said is む. 帰ろう = 帰らむ, 食べよう = 食べむ, しよう = せむ. The "let's / I'll" auxiliary isn't modern at all — it's the oldest layer of the language, still doing conjecture-and-volition duty on your lips.

The 〜ん survival — and a crucial fork

む also contracted a second way: straight to the syllabic nasal ん. This raw ん survives across registers, but here English speakers must be careful, because ん in modern Japanese has two different classical ancestors, and only one of them is む:

む → ん: the volitional / conjectural ん — いざ行かん, さもありなん, 〜んとする, 〜んがため.
ぬ・ず → ん: the negative ん — 知らん, 分からん, できん (casual/dialectal "don't know," from 知らぬ → 知らん).

So 知らん and 分からん, which look like they could be む, are almost always the negative ん (covered on the ず / ぬ / ざる page) — "I don't know," not "I shall know." The verb せん is genuinely ambiguous: せん can be しよう (volitional む) in a formal/literary frame, or しない (negative ぬ) in casual Kansai-flavoured speech. Context decides.

そんなことは知らん。

sonna koto wa shiran

I don't know anything about that. (casual — negative ん, from 知らぬ, NOT volitional む)

さもありなん。

samo ari nan

That may well be so; no wonder. (literary — volitional/conjectural む: な = 完了ぬ未然 + ん = む)

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When you meet 〜ん, sort it by sense: "I don't …" → negative ん (from ぬ/ず); "let's / shall / about to …" → volitional ん (from む). 知らん = negative; いざ行かん = volitional. They are homophones from opposite auxiliaries.

む intact in modern formal Japanese: 〜んとする, 〜んがため

Two literary constructions keep む (as ん) fully alive in editorials, speeches, and elevated prose.

〜んとする / 〜んとす = む + と + す, "to be about to," "to strive to." It is the formal ancestor of modern 〜（よ）うとする.

政府は目標を達成せんとする姿勢を崩さなかった。

seifu wa mokuhyō o tassei sen to suru shisei o kuzusanakatta

The government did not abandon its stance of striving to achieve the goal. (editorial register)

消えなんとする蝋燭の炎を、彼女はじっと見つめていた。

kienan to suru rōsoku no honō o, kanojo wa jitto mitsumete ita

She gazed steadily at the candle flame that was about to go out. (literary)

〜んがため（に） = む + が + ため, "in order to," "for the sake of …-ing." Note the particle: after ん it is が, not の — 勝たんがため, never 勝たんのため.

勝たんがために、彼は毎日練習を重ねた。

katan ga tame ni, kare wa mainichi renshū o kasaneta

In order to win, he piled up practice day after day. (formal)

生きんとする強い意志が、その目に宿っていた。

ikin to suru tsuyoi ishi ga, sono me ni yadotte ita

A powerful will to live dwelt in those eyes. (literary)

You will also meet む's volition in fossilized prayer and rallying language: 願（ねが）わくは…せんことを ("I pray that … may come to pass") and the interjection いざ + 〜ん ("come, let us …").

願わくは、この願いの叶わんことを。

negawaku wa, kono negai no kanawan koto o

I pray that this wish may be granted. (formal / liturgical)

The distinguishing insight: it's all one auxiliary

Learners collect these as unrelated items: the "volitional 〜う・よう" in chapter 8, the "casual 〜ん" somewhere in a dialect note, and "〜んとする / 〜んがため" as advanced reading vocabulary. They are the same word, む, at three stages of erosion:

Fully worn → 〜う・よう (everyday volitional)
Nasalized, colloquial → 〜ん (in いざ行かん, さもありなん)
Nasalized, preserved in set frames → 〜んとす, 〜んがため (formal/literary)

Recognizing this means that when you read 願わくは…せんことを or 勝たんがため, you don't file them as mysteries — you hear volition, the same impulse behind しよう. One auxiliary, many coats.

Common mistakes

❌ 知らん

shiran

❌ Misread as volitional 'I shall know / I intend to know.' — Wrong ancestor: casual 知らん is the NEGATIVE ん (from 知らぬ).

✅ 知らん

shiran

✅ 'I don't know.' — the negative ん; the volitional of 知る would be 知ろう.

The nasal ん has two sources. Meaning-test it: "don't …" is the negative branch; "let's / about to …" is the む branch.

❌ 勝たんのために練習する。

katan no tame ni renshū suru

Wrong particle — after the volitional ん the fixed frame uses が: 勝たんがため, not 勝たんのため.

✅ 勝たんがために練習する。

katan ga tame ni renshū suru

to practice in order to win

❌ 明日、みんなでご飯を食べんとする。

ashita, minna de gohan o taben to suru

✅ 明日、みんなでご飯を食べよう。

ashita, minna de gohan o tabeyō

Let's all eat together tomorrow.

❌ 帰ろう

kaerō

❌ Filed as a modern-only form with no history. In fact 帰ろう IS classical む: 帰らむ → 帰らう → 帰ろう.

✅ 帰らむ

kaeramu

✅ the classical ancestor of 帰ろう — one auxiliary, む, at two stages of wear.

❌ 行くむ

Wrong stem — む attaches to the 未然形, not the 終止形. It's 行か + む, not 行く + む.

✅ 行かむ

ikamu

let's go / I'll go / (it) will go

Key takeaways

む attaches to the 未然形 and fuses conjecture, volition, and invitation into one form; むず (む + と + す) is its emphatic twin.
Modern 〜う・よう is む worn down: 行かむ → 行こう, せむ → しよう. You use む every day.
The nasal ん has two ancestors: volitional む (いざ行かん, さもありなん) and negative ぬ/ず (知らん, 分からん). Sort by meaning.
む stays intact in formal 〜んとする ("about to / strive to") and 〜んがため ("in order to" — note the が), live in editorials and speeches.
Seeing 〜う・よう, 〜ん, and 〜んとす as one auxiliary turns a pile of "unrelated endings" into a single, recognizable idea: projected, willed, not-yet-real action.

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