From HomoExcelsior

1. The even or odd quality of an integer. If two integers are both odd or both even, they are said to have the same parity; if one is odd and one even, they have different parity. 2. An intrinsic symmetry property of subatomic particles that is characterized by the behavior of the wave function of such particles under reflection through the origin of spatial coordinates. 3. A quantum number, either +1 (even) or -1 (odd), that mathematically describes this property. 4. The even or odd quality of the number of 1's or 0's in a binary code, often used to determine the integrity of data especially after transmission. 5. A parity bit.

For example, memory chips may include a parity bit attached to each byte to help automate detection of failure. Serial communication using RS-232 can have an extra parity bit turned on as an extra data check to ensure communication is uncorrupted.

Implementation in serial transmittion protocols is simply achieved by toggling a flip-flop when a 1 (on-bit) is received as the stream arrives.

See also: CRC (cyclic redundancy check)

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