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1570s, "equality of rank or status," from Middle French parité (14c.) or directly from Late Latin paritas "equality," from Latin adjective par (genitive paris) "equal" (see pair (n.)). Meaning "condition in which adversaries have equal resources" is from 1955, originally in reference to the U.S.A. and the U.S.S.R.
parity par·i·ty (pār'ĭ-tē)
The state of having given birth to an infant or infants.
An extra bit added to a byte or word to reveal errors in storage (in RAM or disk) or transmission. Even (odd) parity means that the parity bit is set so that there are an even (odd) number of one bits in the word, including the parity bit. A single parity bit can only reveal single bit errors since if an even number of bits are wrong then the parity bit will not change. Moreover, it is not possible to tell which bit is wrong, as it is with more sophisticated error detection and correction systems.
See also longitudinal parity, checksum, cyclic redundancy check.