‘Error’ and ‘Mistake’ are two of these words. Both of the words mean: “A wrong action attributable to bad judgment, or ignorance. Both are fall into the same category. It is highly acceptable to use ‘error’ in formal or technical contexts. In scientific or highly technical terms, the word ‘error’ is more suitable. In the world of computing and programming, ‘error’ is the more fitting term to indicate a mistake, or fault, particularly in coding and processes. ‘System Error’ sounds better than ‘System Mistake’, doesn’t it? Mistake’, on the other hand, is used more in casual English conversation. Though ‘error’ may still be used in exchange, it will often sound unnatural, or technicalese. It would be awkward to say something like: “It was all an error. I am sorry!”, to your girlfriend. The more natural sounding statement would be: “It was all a mistake. I am sorry!”