# ammonium

/əˈmoʊniəm/ (US) · /æmˈəʊniəm/ (UK) · CEFR C1 · Noun

Source: https://englishreference.com/word/ammonium
Updated: 2026-05-11

## Definition

a chemical part made of nitrogen and hydrogen that is found in many fertilizers and cleaning products. It is often part of a larger chemical compound rather than existing on its own.

For teachers: a positively charged polyatomic ion with the chemical formula NH4+. It is formed by the protonation of ammonia and typically exists as a component in various salts and chemical compounds.

## Examples

- The soil test showed high levels of ammonium.
- Farmers often apply ammonium nitrate to their fields to provide essential nitrogen for crop growth.
- In aquatic environments, the balance between ammonia and ammonium is highly dependent on the pH level, with more acidic water shifting the equilibrium toward the less toxic ion.

## Usage notes

- Usually functions as a modifier in chemical names like 'ammonium chloride' or 'ammonium nitrate'.

---

From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.