不知不觉

不知不覺
bùzhī-bùjué

unconsciously; unwittingly

Wiktionary

Homographs

不知不觉 bùzhībùjué (idiom) unconsciously; unwittingly

Examples

天不知不觉地暗了下来。

It became dark before I knew it.

Source: Tatoeba

Entry Composition

1 不知 bùzhī
  1. not to know
  2. unaware
  3. unknowingly
  4. fig. not to admit (defeat, hardships, tiredness etc)
2 不觉 bùjué unconsciously