Plural of ammonium; multiple instances of the positively charged ion NH4+, or ammonium compounds.
From ammonium (ammonia plus -ium, a suffix for chemical elements and ions) plus the regular English plural -s. This chemical term became standardized as ammonium compounds became essential in industry and agriculture.
Ammonium ions are the chemical bridges between sky and soil—lightning fixes nitrogen into ammonia, bacteria convert it to ammonium, and plants finally get something they can eat.
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