Error
An error has different meanings in different domains. Current meanings in some of those domains are described below. The Latin word error meant "wandering" or "straying".
An error is a difference between a computed, estimated, or measured value and the true, specified, or theoretically correct value. See also errors and residuals in statistics.
Experimental Science
An error is a bound on the precision and accuracy of the result of a measurement. These can be classified into two types: statistical error (see above) and systematic error. Statistical error is caused by random (and therefore inherently unpredictable) fluctuations in the measurement apparatus, whereas systematic error is caused by an unknown but nonrandom fluctuation. If the cause of the systematic error can be identified, then it can usually be eliminated.
An error is a difference between desired and actual performance. Engineers often seek to design systems in such a way as to mitigate or even avoid the effects of error. See also Observational error
An error is a deviation from a correct value caused by a malfunction in a system or a functional unit. An example would be the occurrence of a wrong bit caused by an equipment malfunction. (Sources: Federal Standard 1037C and MIL-STD-188). See also error-correcting code and error-detecting code
An error is incorrectly written code, usually not intentional. There are two major types of error. The syntax error is easiest to detect since the code will not compile properly and cannot be parsed. The logical error is more difficult to solve since it involves the working of the actual code. Both types of error can create an error avalanche, which is caused by the now broken code continuing to affect subsequent code. See also : error handling.
An individual language user's deviations from standard language paradigms are sometimes referred to as errors. At present, this usage is out of favor outside of language classes. Those who recognize the role of language usage in everyday social class distinctions feel that linguistics should be descriptive rather than prescriptive to avoid reinforcing dominant class value judgements about what linguistic forms should and should not be used.
An error is said to occur when perfect fidelity is lost in the copying of information. For example, in an asexually reproducing species, an error (or mutation) has occurred for each DNA nucleotide that differs between the child and the parent. Errors in this sense are not judged as "good" or "bad", although an error may make an organism either more or less adapted to its environment.
An error is judged by the official scorer when a runner advances a base because of a fielding mistake, and perfect play would have prevented the advancement, and the mistake was physical. Mental misjudgements are not errors. Failing to get more than one out on given play is not an error. Application of this rule is necessarily subjective. See error (baseball).