A typographical error (often shortened to typo) is a mistake made in the typing process (such as a spelling mistake) of printed material. historically, this referred to mistakes in manual type-setting (typography). the term includes errors due to mechanical failure or slips of the hand or finger, but excludes errors of ignorance, such as spelling errors. 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. fat finger, or "fat-finger syndrome", a slang term, refers to an unwanted secondary action when typing. when one's finger is bigger than the touch zone, there can be inaccuracy in the fine motor movements and accidents occur. this is common with touchscreens. one may hit two adjacent keys on the keyboard in a single keystroke. an example is buckled instead of bucked, due to the l key being next to the k key on many keyboards.