auxiliary verb
without doing; not doing; not ... and
Classical continuative negative auxiliary. Attaches to the -nai stem of verbs (for サ変, せ~ず). Functions like 'without doing' or 'not ... and/so', often in formal or written language. See also ずに.
彼は何も言わずに部屋を出て行った。
He left the room without saying anything.
準備をせずに試験を受けるのは無謀だ。
Taking an exam without preparing is reckless.
auxiliary verb
Archaic sentence-ending negative, equivalent to modern ない. Rarely used in modern Japanese except in set phrases or classical contexts.
See also: ない
「知らぬ」の「ぬ」は、古い言い方で「知らず」とも言う。
The ぬ in 知らぬ is an old form, also expressed as 知らず.