What is the meaning of Không?

zero

river

Negates the meaning of the stated verb or adjective: not

not at all

idly; without doing anything else

at a level that feels like nothing at all

only, without anything else

empty

air; space; nothing

(Can we verify this sense?) Clipping of không trung (the air).

the intangible, non-material aspect

no

yes

or else

Used to form polar questions, placed at the end of a question

Used as an answer of refutation to a polar question: no

zero

Source: wiktionary.org