aionios

Aionios (Greek: αἰώνιος) is a Greek adjective usually rendered in English as "eternal," "everlasting," or "age-long." It derives from aiōn, meaning "age" or "lifetime," with the suffix -ios, producing a sense of enduring duration. In classical Greek, aionios often means lasting for an age or belonging to a particular era; it can denote long but finite durations as well as the more expansive sense of perpetuity, depending on context. The word is cognate with the English "aeon" (or "eon") and with terms in other languages that express long or infinite time.

In Koine Greek, which underlies much of the Greek New Testament, aionios takes on a specialized theological range. It frequently translates the Hebrew term olam and is used in phrases such as aionion zoe ("eternal life") and aionion kolasis ("eternal punishment"). English translations vary: some render the phrase as "eternal" or "everlasting," while others prefer "age-abiding" or "age-lasting" to reflect contextual nuance. The use of aionios has been a subject of scholarly and theological discussion, particularly regarding whether it denotes infinite duration or, in some contexts, an extended but finite period.

Today, the form remains part of Modern Greek as a general adjective meaning "eternal" or "everlasting." In scholarly writing about ancient languages, aionios is treated as a key example of how Greek lexical choices encode duration, eternity, and the interplay between language and theology.