〜ぬ nu
〜ぬ（nu）means “not (classical/literary negative)”. A classical/literary negative auxiliary equivalent to ～ない. Formation: V（ない形）の「ない」を「ぬ」に替える ※「する」→「せぬ」
not (classical/literary negative)
N2Formation
V（ない形）の「ない」を「ぬ」に替える ※「する」→「せぬ」
Explanation
A classical/literary negative auxiliary equivalent to ～ない. Sounds old-fashioned, formal or proverbial; survives in set phrases, signs and written style.
Examples
Note
する → せぬ (not しぬ); the ～ず form (e.g. 知らず) is the related adverbial/continuative shape.
FAQ
〜ぬ — what does it mean and how is it used?
not (classical/literary negative). A classical/literary negative auxiliary equivalent to ～ない. Sounds old-fashioned, formal or proverbial; survives in set phrases, signs and written style.
〜ぬ — how do you form it?
V（ない形）の「ない」を「ぬ」に替える ※「する」→「せぬ」
〜ぬ — any usage notes?
する → せぬ (not しぬ); the ～ず form (e.g. 知らず) is the related adverbial/continuative shape.