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definitions

pyro-

a combining form meaning “fire,” “heat,” “high temperature,” used in the formation of compound words: pyrogen; pyrolusite; pyromancy.
Chemistry. a combining form used in the names of inorganic acids, indicating that the acid's water content is intermediate between that of the corresponding ortho- (more water) and meta- (least water) acids (pyroantimonic, H4Sb2O7, pyroarsenic, H4As2O7, and pyrosulfuric, H2S2O7, acids). The combining form is also used in the names of the salts of these acids. If the acid ends in -ic, the corresponding salt ends in -ate (pyroboric acid, H2B4O7, and potassium pyrobate, K2B4O7, or pyrosulfuric, H2S2O7, and pyrosulfate, N2S2O7); if the acid ends in -ous, the corresponding salt ends in -ite (pyrophosphorous acid, H4P2O5, potassium pyrophosphite, K4P2O5).
Also pyr-.

Origin of pyro-

< Greek pyro-, combining form of pŷr fire
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for pyro-

pyro-

before a vowel pyr-

combining form

denoting fire, heat, or high temperaturepyromania; pyrometer
caused or obtained by fire or heatpyroelectricity
chem
  1. denoting a new substance obtained by heating anotherpyroboric acid is obtained by heating boric acid
  2. denoting an acid or salt with a water content intermediate between that of the ortho- and meta- compoundspyro-phosphoric acid
mineralogy
  1. having a property that changes upon the application of heatpyromorphite
  2. having a flame-coloured appearancepyroxylin

Word Origin for pyro-

from Gk pur fire
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
Word Origin and History for pyro-

before vowels pyr-, word-forming element form meaning "fire," from Greek pyro-, combining form of pyr (genitive pyros) "fire, funeral fire," also symbolic of terrible things, rages, "rarely as an image of warmth and comfort" [Liddell & Scott]; see fire (n.). Pyriphlegethon, literally "fire-blazing," was one of the rivers of Hell.

Online Etymology Dictionary, © 2010 Douglas Harper
pyro- in Medicine

pyro-

pref.

Fire; heat:pyrophobia.
Relating to the action of fire or heat:pyrolysis.
Fever:pyrogen.
Derived from an acid by the loss of a water molecule:pyrophosphoric acid.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.