-ion

Etymology

It is inherited from Middle English -ioun, also -ion and -iun,^[2][3] borrowed from Anglo-Norman -ion and Old French -ion, and directly borrowed from Latin -iō, stem -iōn-,^[4][5][2][6] a suffix that formed nouns of condition and action.^[4][6][3] In Latin it was added most often to past participle or supine stems in -t-, -s- and -x-, as in actiō, missiō and solūtiō, and sometimes to the main verb stem, as in legiō and opīniō; formations on adjectives or nouns, such as commūniō, are rare.^[4][6]

Earliest recorded meaning

There are occasional borrowings from Latin before the Norman Conquest, such as passion and procession; words of this type came in very often in Middle English, directly from Latin or more usually through French.^[4]

Semantic evolution

Words formed within English, chiefly on verbs ultimately from Latin, become common only from the 16th century, and mostly follow the patterns -ation and -ition.^[4] The endings usually written as a unit, -tion, -sion and -xion, reflect the Latin participial stems.^[4][7][6] Besides an action, such nouns can name an instance of it (a suggestion), or a resulting state or product (vexation, concoction).^[7][2] Some words have no underlying English verb, as with onion and union.^[3]

Timeline

• Old English – occasional borrowings: passion, procession.^[4]
• Middle English – very frequent borrowings, usually through French, mainly in -tion, -sion, -xion.^[4]
• 16th century – formations within English become common.^[4]

Meanings

Suffix

1. Forming nouns for an action or process: invention, rebellion.^[8][2][7]
2. Forming nouns for the result of an action: decision.^[2][7][3]
3. Forming nouns for a state or condition: isolation.^[8][2]

Word family

• action
• communion
• legion
• opinion
• mission

Related words

• -ation
• -tion
• -sion
• -ition

Usage notes

The OED also has three unrelated technical suffixes of this form.^[4] One names points on the skull (inion, rhinion), from French, after Broca in 1875.^[4] One names ions (hydrion, sodion), from ion, after a suggestion made to Faraday by J. F. Daniell in 1840, and is found from 1856.^[4] One names plant alliances, from French in 1922 and in English from 1930, and is of unknown origin.^[4]

References

1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
3. ^ a b c d Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
4. ^ a b c d e f g h i j k l m Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
5. ^ Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
6. ^ a b c d Hoad, T. F., ed. (1986), The Concise Oxford Dictionary of English Etymology, Oxford: Clarendon Press
7. ^ a b c d Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
8. ^ a b Collins English Dictionary (2023), Glasgow: HarperCollins