Relating to or lasting for an aion; eternal or existing for an extremely long period of time.
From 'aion' (Greek 'aiōn') plus the adjectival suffix '-ial.' This term is sometimes used in theological contexts to describe eternal or age-long qualities.
You'll rarely see 'aionial' in modern English—'eternal' and 'sempiternal' have won the popularity contest—but it appears in some religious philosophical texts trying to describe God's relationship to time in a more nuanced way than simple 'forever.'
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