Definition of alkali in English:

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Pronunciation: /ˈalkəˌlī/

noun (plural alkalis)

A chemical compound that neutralizes or effervesces with acids and turns litmus blue; typically, a caustic or corrosive substance of this kind such as lime or soda. Often contrasted with acid; compare with base1.

Alkalis release hydroxide ions (OH-) when dissolved in water. An alkaline solution has a pH greater than 7.

Example sentences
  • Amides are hydrolysed to ammonium salts with catalysis by acids or alkalis.
  • They resist most chemicals, including many acids, alkalis, oxidizing agents, and solvents.
  • Nickel has good resistance to corrosion in the normal atmosphere, in natural freshwaters and in deaerated nonoxidizing acids, and it has excellent resistance to corrosion by caustic alkalis…


Late Middle English (denoting a saline substance derived from the ashes of various plants, including glasswort): from medieval Latin, from Arabic al-ḳalī 'calcined ashes (of the glasswort, etc.)', from ḳalā 'fry, roast'.

  • The chemistry term alkali is from medieval Latin, from Arabic al-kalī ‘calcined ashes’ referring to the plants from which alkalis were made. Early 19th-century alkaloid (a class of compounds including morphine, quinine, and strychnine) was coined in German from alkali.

For editors and proofreaders

Syllabification: al·ka·li

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