ammonium

noun

am·​mo·​ni·​um ə-ˈmō-nē-əm How to pronounce ammonium (audio)
: an ion NH4+ derived from ammonia by combination with a hydrogen ion and known in compounds (such as salts) that resemble in properties the compounds of the alkali metals

Examples of ammonium in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Two additional organic ammonium salts — N,N-dimethyloctylammonium iodide (DMOAI) and phenethylammonium chloride (PEACl) — stabilised the material’s ions, stopping them from separating into different phases that hurt efficiency. Aamir Khollam, Interesting Engineering, 11 Aug. 2025 Many Japanese straightening treatments do not include bisphenol A and formaldehyde, but do include ammonium thioglycolate which is a chemical that can cause significant skin irritation and damage scalp health. Cierra Black, Essence, 17 July 2025 Hartford Courant There are other factors that can affect calcium uptake by the plant, such as high concentrations of ammonium, potassium, and magnesium in the soil. Nora Doonan, Hartford Courant, 14 June 2025 Iran also sources critical missile-fuel chemicals—such as ammonium perchlorate—from China, importing thousands of tons in recent months. Amir Daftari, MSNBC Newsweek, 12 June 2025 See All Example Sentences for ammonium

Word History

Etymology

New Latin, from ammonia

First Known Use

1808, in the meaning defined above

Time Traveler
The first known use of ammonium was in 1808

Cite this Entry

“Ammonium.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/ammonium. Accessed 10 Sep. 2025.

Kids Definition

ammonium

noun
am·​mo·​ni·​um ə-ˈmō-nē-əm How to pronounce ammonium (audio)
: an ion that comes from the combination of ammonia with a hydrogen ion

Medical Definition

ammonium

noun
am·​mo·​ni·​um ə-ˈmō-nē-əm How to pronounce ammonium (audio)
: an ion NH4+ derived from ammonia by combination with a hydrogen ion and known in organic compounds (as quaternary ammonium compounds) and in compounds (as salts) that resemble in properties the compounds of the alkali metals
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