A variant spelling of 'aeon,' meaning an extremely long period of time or an eternal age.
From Greek 'aiōn' meaning 'age' or 'eternity.' This spelling variant reflects the direct Greek transliteration, though 'aeon' and 'eon' are now more common in English.
The spelling 'aion' preserves the original Greek diphthong 'ai' that most English speakers have smoothed into the simpler 'eon'—it's like fossils in spelling that show us how English absorbed Greek words.
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