ERROR (Lat. error, from errare, to wander, to err), a mistake, a departure or deviation from what is true, exact or right. For the legal process by which a judgment could be reversed on the ground of error, known as a “writ of error,” see Writ and Appeal. The words “error excepted” or “errors and omissions excepted” (contracted to “E.E.” “E. & O.E.”), are frequently placed at the end of a statement of account or an invoice, so that the accounting party may reserve the right to correct any errors or omissions which may be subsequently discovered, or make further claims in respect of them. In mathematics, “error” is the deviation of an observed or calculated quantity from its true value. The calculus of errors leads to the formulation of the “law of error,” which is an analytical expression of the most probably true value of a series of discordant values (see Probability).