anion

Etymology

It is borrowed from Ancient Greek ἀνιόν (anión, “(a thing) going up”),^{[2][3][4][5][6]} the neuter of ἀνιών (aniṓn), present participle of ἄνειμι (áneimi, “to go up”),^[1][5][7] from ἀνά (aná, “up”) and εἶμι (eîmi, “to go”),^[2][1] from Proto-Indo-European *ei- (“to go”).^[8][3] Some dictionaries instead analyse it as English ana- or anode with ion.^[9][10][11] William Whewell proposed the word and Michael Faraday published it,^[8][1] though Barnhart and Klein credit Faraday alone.^[4][5]

Earliest recorded meaning

An ion that moves to the anode in electrolysis: on 5 May 1834 Whewell wrote, "I would propose for the two elements resulting from electrolysis the terms anion and cation,..and for the two together you might use the term ions."^[2]

Semantic evolution

The Greek sense "going up" was applied to the ion that moves to the anode.^[2][8] Merriam-Webster Unabridged now puts first the general sense of any negatively charged ion, as hydroxide, chloride or acetate, and also lists a negative gaseous ion.^[6] Among later compounds, anion exchange is recorded from 1931.^[2]

Timeline

• 1834 – an ion moving to the anode in electrolysis.^[2][4][6][8]
• 1931 – in anion exchange, ion exchange involving anions.^[2]

Meanings

Noun

1. A negatively charged ion, as of chloride or hydroxide; the opposite of a cation.^[9][6][11]
2. In electrolysis, an ion that migrates to the anode.^[9][6][2]
3. A negative gaseous ion.^[6]

Word family

• anionic
• anionically
• carbanion

Related words

• anode
• anodic
• ion
• cation
• ana-
• exit
• issue

References

1. ^ a b c d e Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
4. ^ a b c Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
5. ^ a b c Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
6. ^ a b c d e f Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
7. ^ Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
8. ^ a b c d Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
9. ^ a b c Collins English Dictionary (2023), Glasgow: HarperCollins
10. ^ Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
11. ^ a b Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press