Type I and type II errors

Statistical error: the difference between a computed, estimated, or measured value and the true, specified, or theoretically correct value (see errors and residuals in statistics) that is caused by random , and inherently unpredictable fluctuations in the measurement apparatus. [2]
Systematic error: the difference between a computed, estimated, or measured value and the true, specified, or theoretically correct value that is caused by non-random fluctuations from an unknown source (see uncertainty), and which, once identified, can usually be eliminated. [2]

Type I errors (or α error, or false positive) and type II errors (β error, or a false negative) are two terms used to describe statistical errors.