There are multiple definitions - click on the translation that matches your context.

błąd

rzeczownik

full

mistake

noun

Definitions of mistake

(CONTRACT LAW) an incorrect belief, at the time of contracting, that certain facts are true. It may be used as grounds to nullify (=make legally null and void; invalidate) the agreement.

A contract may be void if there is a mistake in the identity of the contracting party.

an error or unintentional act

An NHS (=UK National Health Service) trust has been ordered to apologise personally to relatives of a man who bled to death after a mistake during surgery.