parity bit

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A bit added to a binary code that indicates parity and is used to check the integrity of data.

from the GNU version of the Collaborative International Dictionary of English.

• noun (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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun computing A bit (binary digit) used to indicate whether the number of bits in a given set with value of one is even or odd. Parity bits are used as a simple error detection code.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun (computer science) a bit that is used in an error detection procedure in which a 0 or 1 is added to each group of bits so that it will have either an odd number of 1's or an even number of 1's; e.g., if the parity is odd then any group of bits that arrives with an even number of 1's must contain an error