A typographical error, also called a misprint, is a mistake made in the typing of printed or electronic material. Historically, this referred to mistakes in manual typesetting. Technically, the term includes errors due to mechanical failure or slips of the hand or finger, but excludes errors of ignorance, such as spelling errors, or changing and misuse of words such as "than" and "then". Before the arrival of printing, the copyist's mistake or scribal error was the equivalent for manuscripts. Most typos involve simple duplication, omission, transposition, or substitution of a small number of characters.