NOTE: implies an actor/agent's thought or belief which is incorrect
She made the mistake of thinking that Bob could influence John's opinion.
Make no mistake, they will use their nuclear weapons if pressed hard enough.
Their mistake was believing that John was the same man seen in front of the bank last night.
There is no mistake, my wallet was stolen from my purse at the restaurant. (my belief is not wrong)
WordNet 3.0 Sense Numbers: 2, 3
NOTE: implies an external result or consequence that is viewed as an error
NOTE: -not- a state of mind of someone (Sense 1)
The skater was marked down by the judges for two mistakes in her long routine.
I found several spelling mistakes in the manuscript.
That mistake during surgery cost the surgeon his medical license.
I left my purse by mistake at the restaurant last night. (my action was in error, -not- my belief)
Inviting them both to this party was a mistake.
WordNet 3.0 Sense Numbers: 1