"Typo" is short for typographical error. A typographical error is one that is made in a document when it is typed or printed using a computer or typewriter. It is an error that would not occur if the material was handwritten. Unidentified sources, overuse of quotations and poor word choice are all mistakes that are made by the author and relate to his judgement. Missing and repeated words, on the other hand, can occur simply from the misuse of a mechanical device.
