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).