不知

not to know / unaware / unknowingly / fig. not to admit (defeat, hardships, tiredness etc)

no; not so / (bound form) not; un-

to know / to be aware

unconsciously / unwittingly

whereabouts unknown / gone missing

to know nothing about the beginning, the middle or the end / to know nothing at all

a person who doesn't manage a household would not be aware how expensive it is (idiom)

forgetting the fate of Ding and Dong (idiom) / unheeding the lessons of the past

It's a long and intricate story, I hardly know where to start.

lit. to reply "don't know" whatever the question (idiom) / fig. absolutely no idea of what's going on / complete ignorance

somehow

one can't tell how many / numerous similar cases

see 不知好歹[bu4 zhi1 hao3 dai3]