parity

Etymology 1

From Middle French parité, from Late Latin paritas, from Latin pār (“equal”). Equivalent to pari- + -ty.

noun

1. (uncountable) Equality; comparability of strength or intensity.
   Altogether, Microsoft claims a 99% feature parity between 32-bit and 64-bit editions. 2000 April 26, Microsoft Windows Server 2003 Delta Guide, Pearson Education, unpaged
   For all their frailty at the back, Arsenal possessed genuine menace in attack and they carved through Chelsea with ease to restore parity nine minutes before half-time. Aaron Ramsey's pass was perfection and Gervinho took the unselfish option to set up Van Persie for a tap-in. October 29, 2011, Phil McNulty, “Chelsea 3 - 5 Arsenal”, in BBC Sport
2. Senses related to classification into two sets.
   1. (mathematics, countable) A set with the property of having all of its elements belonging to one of two disjoint subsets, especially a set of integers split in subsets of even and odd elements.
      Parity is always preserved in such operations.
   2. (mathematics, countable) The classification of an element of a set with parity into one of the two sets.
      The particles' parities can switch at random.
   3. (computing) The count of one bits in a value, reduced to even or odd or zero or one.
   4. (physics, countable) Symmetry of interactions under spatial inversion.
3. (games, countable) In reversi, the last move within a given sector of the board.
4. Resemblance; analogy.

Etymology 2

From Latin paritas, from pariō (“give birth”).

noun

1. (medicine, countable) The number of delivered pregnancies reaching viable gestational age, usually between 20-28 weeks
2. (agriculture, countable) The number of times a sow has farrowed.