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a. Action or process: completion.
b. Result of an action or process: indention.
2. State or condition: dehydration.

[Middle English, from Old French, from Latin -iō, -iōn-, n. suff.]


suffix forming nouns
indicating an action, process, or state: creation; objection. Compare -ation, -tion
[from Latin -iōn-, -io]


(ˈaɪ ən, ˈaɪ ɒn)

1. an atom or atom group electrically charged by the loss or gain of electrons, represented by a plus or a minus sign, as a cation (Na + , Ca + + ) or anion (Cl).
2. one of the electrically charged particles formed in a gas by electric discharge.
[< Greek ión going, neuter present participle of iénai to go; term introduced by Michael Faraday in 1834]
i•on′ic, adj.


a suffix, appearing in words of Latin origin, denoting action or condition, used to form nouns from stems of adjectives (communion; union) and verbs (legion; opinion; suspicion).
Compare -tion.
[Middle English -ioun < Anglo-French < Latin -iōnem, acc. of -iō suffix forming nouns]