a very small amount 一点点；很少量；丝毫 She hadn't changed a whit since I'd seen her last. 自从我上次见到她以来，她一点也没变。
Word Originlate Middle English: apparently an alteration of obsolete wight ‘small amount’.
Idioms
not a whit | not one whit
not at all; not the smallest amount 丝毫不；一点不 The result should surprise us not one whit. 结果一点也不会让我们吃惊。