n. [ L. paritas, fr. par, paris, equal: cf. F. parité. See Pair, Peer an equal. ] 1. The quality or condition of being equal or equivalent; a like state or degree; equality; equivalence; close correspondence; analogy; as, parity of reasoning. “No parity of principle.” De Quincey. [ 1913 Webster ]

Equality of length and parity of numeration. Sir T. Browne. [ 1913 Webster ]

2. Specifically: (Finance) Equivalence in value to the currency of another country. [ PJC ]

3. (Physics) A property assigned to elementary particles, conceptualized as a form of symmetry, representing the fact that no fundamental distinctions can be observed between right-handed and left-handed systems of particles in their interactions, and supported by the typical observation that the total parity of a system is unchanged as particles are created or annihilated; however, certain interactions involving the weak force have been shown to violate the principle of conservation of parity. [ PJC ]

4. (Physics) A property of the wave function of a system, which takes the value of +1 or -1, indicating whether the value of the wave function changes sign if each of the variables of the system is replaced by its negative. [ PJC ]

5. (Med.) The condition of having borne a child or children, alive or dead. [ PJC ]

6. (Math.) The property of being even or odd; as, 3 has odd parity, but 6 has even parity. [ PJC ]

7. Hence: (Computers) The property of having an even or odd number of bits set to the value of 1 (as opposed to 0); -- applied to bytes or larger groups of bits in a data structure. It is used mostly in the process of parity checking. The parity of a data structure can be changed by changing the value of the parity bit. [ PJC ]

n. (Computers) The bit within a data structure which is assigned a value of 1 or 0 so as to make the parity{ 7 } of the data structure odd or even. Data structures may or may not have parity bits, dpending on whether the system does or does not perform parity checking. The most commonly used parity bit is the eigth (higher-order) bit of a byte, which is used when data transmission uses only the 7 lower-order bits of each byte as significant data; some memory systems use a ninth bit as a parity bit for each eight bits (one byte) of significant data in memory. [ PJC ]

n. (Computers) The act or process of testing whether a byte or other data structure has an even or odd number of bits set to the value of 1; -- it is used primarily to detect errors in data, especially in memory banks or in data transmitted over a communications line. The parity can be changed by assigning one bit in each data structure as the parity bit, so that the total number of bits set to the value of 1 is odd (odd parity) or even (even parity). If parity is used for error checking the writing and reading systems must first agree on which type of parity (odd or even) to use; if the reading system detects a deviation from the agreed parity, it signals an error, to be handled by the error-handling processes of the system. [ PJC ]

n. (Computers) The process of performing a parity check. [ PJC ]