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-onium

American

Chemistry.

a suffix used in the names of complex cations.

oxonium.

Etymology

Origin of -onium

Extracted from ammonium

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Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.