Parity

“Parity” often comes up in error control as there is a well-known method based on it. The word "parity" has a general meaning of simply saying if a number is even or odd. It comes from the same root word as “pair” – even parity means that there is an even number of objects (they can be put in pairs), and odd parity means they can’t be put into pairs. If you have 5 white socks, then they have odd parity, but you want them to have even parity! The system described in lesson plan one uses even parity, as it is slightly easier to work with in this situation; so "even parity" is just a fancy way of saying that there is an even number of something.