[par-uh-hahy-druh-juh n]
noun Physics, Chemistry.
  1. the form of molecular hydrogen in which the nuclei of the two hydrogen atoms contained in the molecule have spins in opposite directions.
Compare orthohydrogen.

Origin of parahydrogen

First recorded in 1925–30; para-1 + hydrogen Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for parahydrogen

Historical Examples of parahydrogen

  • If they are oriented in opposite directions, it is parahydrogen.

    Unwise Child

    Gordon Randall Garrett

British Dictionary definitions for parahydrogen


  1. chem the form of molecular hydrogen (constituting about 25 per cent of the total at normal temperatures) in which the nuclei of the two atoms in each molecule spin in opposite directionsCompare orthohydrogen
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012