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, H ₄ Sb ₂ O ₇ , pyroarsenic, H ₄ As ₂ O ₇ , and pyrosulfuric, H ₂ S ₂ O ₇ , 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, H ₂ B ₄ O ₇ , and potassium pyrobate, K ₂ B ₄ O ₇ , or pyrosulfuric, H ₂ S ₂ O ₇ , and pyrosulfate, N ₂ S ₂ O ₇ ); if the acid ends in -ous, the corresponding salt ends in -ite (pyrophosphorous acid, H ₄ P ₂ O ₅ , potassium pyrophosphite, K ₄ P ₂ O ₅ ).