expression
exactly; perfectly; without the slightest difference
Emphasizes that something matches or is reproduced with absolute precision, down to the smallest detail. Often used in formal or emphatic contexts.
彼は寸分違わず同じ動作を繰り返した。
He repeated the exact same motion without the slightest difference.
このコピーは原本と寸分違わず一致している。
This copy matches the original perfectly.
From 寸 (すん, a very small unit of length) and 分 (ぶん, a fraction of a 寸), combined with 違わず (negative of 違う, 'to differ'), literally meaning 'not differing by even a 寸 or 分'.