Aeon
The word aeon , also spelled eon (in American and Australian English), originally meant "life", "vital force" or "being", "generation" or "a period of time", though it tended to be translated as "age" in the sense of  "ages", "forever", "timeless" or "for eternity". It is a Latin transliteration from the ancient Greek word  (), from the archaic  () meaning "century". In Greek, it literally refers to the timespan of one hundred years. A cognate Latin word  or  (cf. ) for "age" is present in words such as longevity and mediaeval.

Although the term aeon may be used in reference to a period of a billion years (especially in geology, cosmology and astronomy), its more common usage is for any long, indefinite period.  Aeon can also refer to the four aeons on the geologic time scale that make up the Earth's history, the Hadean, Archean, Proterozoic, and the current aeon, Phanerozoic.

Astronomy and cosmology
In astronomy, an aeon is defined as a billion years (109 years, abbreviated AE).
 
Roger Penrose uses the word aeon to describe the period between successive and cyclic Big Bangs within the context of conformal cyclic cosmology.

Philosophy and mysticism

In Buddhism, an "aeon" or  (Sanskrit: ) is often said to be 1,334,240,000 years, the life cycle of the world.

Christianity's idea of "eternal life" comes from the word for life,  (), and a form of  (), which could mean life in the next aeon, the Kingdom of God, or Heaven, just as much as immortality, as in .

According to Christian universalism, the Greek New Testament scriptures use the word  () to mean a long period and the word  () to mean "during a long period"; thus, there was a time before the aeons, and the aeonian period is finite. After each person's mortal life ends, they are judged worthy of aeonian life or aeonian punishment. That is, after the period of the aeons, all punishment will cease and death is overcome and then God becomes the all in each one (). This contrasts with the conventional Christian belief in eternal life and eternal punishment.

Occultists of the Thelema and Ordo Templi Orientis (English: "Order of the Temple of the East") traditions sometimes speak of a "magical Aeon" that may last for perhaps as little as 2,000 years.

Gnosticism

In many Gnostic systems, the various emanations of God, who is also known by such names as the One, the Monad, Aion teleos ("The Broadest Aeon", Greek: ), Bythos ("depth or profundity", Greek: ), Proarkhe ("before the beginning", Greek: ),  ("the beginning", Greek: ),  ("wisdom"), and  ("the Anointed One"), are called Aeons. In the different systems these emanations are differently named, classified, and described, but the emanation theory itself is common to all forms of Gnosticism.

In the Basilidian Gnosis they are called sonships ( ; singular:  ); according to Marcus, they are numbers and sounds; in Valentinianism they form male/female pairs called "" (Greek , from  ).

See also

 Aion (deity)
 
 Kalpa (aeon)
 
 Saeculum – comparable Latin concept

References

New Testament Greek words and phrases
Time
Units of time
Gnosticism