(mathematics) The difference (sometimes defined to be the absolute difference) between the measured or inferred value of a quantity and its true value.

(geometry, geomagnetism) The combination of variation and deviation which is the horizontal angle between the direction indicated by a magnetic compass and true north.

(computing) A message displayed when a failure condition occurs, usually on a computer or device.

(sciences) A bar used on a graph to indicate the range of one standard deviation in the result of an experimental measurement.

(statistics) An expression of the lack of precision in the results obtained from a sample. / An amount, beyond the calculated minimum, added for safety.

(statistics) The error caused by observing a sample instead of the whole population.

(sports, chiefly tennis) A basic error committed in a tactical game, where errors are usually forced by the game strategy.

(statistics) type II error

(statistics) type I error

(statistics) type II error