This is the 10247th most frequent Polish word.
błędu
"Error" or "mistake."
Here, 'błędu' is the genitive singular form of 'błąd,' used to indicate possession or association, meaning 'of an error.'
Znalazłem błędu w mojej pracy.
I found an error in my work.
In this sentence, 'błędu' again is in the genitive singular, showing causation or origin related to 'error.'
Powodem błędu było niedopatrzenie w dokumentach.
The reason for the error was an oversight in the documents.
Once more, 'błędu' is used in the genitive singular, describing the error someone cannot remove or deal with in the context.