Definition:Mistake

Definition
A mistake (as opposed to an error) is an inaccuracy or (deduced) falsehood caused by (ultimately) human fault.

Synonyms include such terms as boob, bloomer, cock-up, bug (computer science), oversight, and other less polite words frequently encountered at the backs of schoolrooms worldwide.

Please feel free to add your own.

Typo
A typo (abbreviation for typographical error) is a mistake arising from pressing the wrong button on the machine via which you are transcribing your thoughts onto a storage medium. These can be corrected by assiduous checking by the writer.

Spello
A spello (abbreviation for spelling mistake) is a mistake caused by inadequate spelling skills of the writer. These can sometimes be corrected by the writer having the self-doubt necessary to occasion the act of referring to a reliable manual, for example, a dictionary. A competent proof-reader (i.e. one whose spelling skills are more comprehensive than the writer) is usually an adequate resource for reducing spelloes.

Homophone Horror
A homophone horror is a mistake caused by the use of a word which sounds the same as, but is spelt differently to, the word intended. A proficient proof-reader is again needed to reduce instances of this sort of mistake.

Both spelloes and typoes can be reduced by mechanical means, e.g. spell-checkers, but these are unreliable. Homophone horrors are not subject to being detected by a spell-checker, although a grammar-checker may catch one (if you're lucky). Devices which interpret semantic meaning may help here, but they are not widely available.

Quotes

 * "Although there are revolutions in mathematics, they are usually changes in viewpoint or philosophy; earlier results do not change -- although the hypotheses needed to prove them may. In fact, there is a word in mathematics for previous results that are later changed; they are called 'mistakes'."