Learn in the textbookLinear Algebra, Calculus, and Error
DefinitionAn error (誤差) is the difference (the gap) between a value obtained by measurement or calculation and the true value.
ExplanationBecause measuring instruments have scales of limited fineness and computers can hold numbers only to a limited number of digits, error usually cannot be brought down to zero. In computer calculations, for instance, rounding error (丸め誤差) arises when a value is trimmed to fit a set number of digits, and absorption (情報落ち) occurs when numbers of very different magnitudes are added or subtracted and the smaller one fails to show up in the result.
AnalogyWhen you measure a desk with a tape measure, anything between two marks has to be judged by eye, so however carefully you measure, a slight gap from the true width remains.
Memory hook"Error" comes from the Latin errare, "to wander": picture measured values wandering around the true value.