potassium

American  

[puh-tas-ee-uhm] / pəˈtæs i əm /

noun

Chemistry.

1. a silvery-white metallic element that oxidizes rapidly in the air and whose compounds are used as fertilizer and in special hard glasses. K; 39.102; 19; 0.86 at 20°C.

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potassium British  

/ pəˈtæsɪəm /

noun

1. a light silvery element of the alkali metal group that is highly reactive and rapidly oxidizes in air; occurs principally in carnallite and sylvite. It is used when alloyed with sodium as a cooling medium in nuclear reactors and its compounds are widely used, esp in fertilizers. Symbol: K; atomic no: 19; atomic wt: 39.0983; valency: 1; relative density: 0.862; melting pt: 63.71°C; boiling pt: 759°C

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potassium Scientific  

/ pə-tăs′ē-əm /

1. A soft, highly reactive, silvery-white metallic element of the alkali group occurring in nature only in compounds. It is essential for the growth of plants and is used especially in fertilizers and soaps. Atomic number 19; atomic weight 39.098; melting point 63.65°C; boiling point 774°C; specific gravity 0.862; valence 1.

2. See Periodic Table

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Other Word Forms

• potassic
  adjective

Etymology

Origin of potassium

From New Latin, dating back to 1800–10; see origin at potassa, -ium

Compare meaning

How does potassium compare to similar and commonly confused words? Explore the most common comparisons:

• potassium vs. sodium
• potassium vs. potassium chloride

Example Sentences

To maximize production, those crops need three main nutrients: nitrogen, phosphate and potassium.

From Salon • Apr. 8, 2026

"Urine does naturally contain all of the nutrients that plants need such as nitrogen, phosphorus and potassium, but it also contains a variety of contaminants," explained Olivia Wilson, NPK Recovery's research and development scientist.

From BBC • Apr. 2, 2026

Some salt substitutes contain potassium, which can build up to dangerous levels in people with kidney disease or those taking certain medications or supplements.

From Science Daily • Mar. 31, 2026

To determine what caused this enrichment in heavier potassium isotopes, the researchers examined three possible factors.

From Science Daily • Feb. 8, 2026

“Thank you, Quentin. This mixture of potassium chlorate and sugar will demonstrate rapid oxidation.”

From "October Sky" by Homer Hickam