Definition of eon in US English:


(British aeon)


often eons
  • 1An indefinite and very long period of time, often a period exaggerated for humorous or rhetorical effect.

    ‘he reached the crag eons before I arrived’
    ‘his eyes searched her face for what seemed like eons’
    • ‘If anything, the holiday season, while a welcome break, is also an annoying interruption in her routine - for she stopped believing in making New Year's resolutions eons ago.’
    • ‘This question, in various forms, has been pondered by physicists and philosophers for eons.’
    • ‘Humankind has built up that understanding over the eons first and foremost by observing phenomena accurately, and then recording the observations assiduously.’
    • ‘It is deep time that makes possible the blind movement of evolution, the massing and honing of minute effects over eons.’
    • ‘A mainstay of building construction for eons, until recent years the product's drab gray mien was considered too cold for all but the most esoteric decorative purposes.’
    • ‘The consciousness of Gods can stretch for eons and eons.’
    • ‘So, the argument goes, over many eons a self-reinforcing, dynamic process emerged: people burned the land, eucalypts thrived, people burned some more.’
    • ‘Over the eons the lunar spin rate has been damped by Earth's gravity, because the Moon's mass distribution is not uniform.’
    • ‘And through the eons there have been long periods of warming and cooling across the globe.’
    • ‘I gathered my feet beneath me and tore forward, screaming a maniacal scream that I think I may have picked up at the academy eons and eons ago.’
    • ‘We have seen how the basic aspects of solar eclipses appear in the sky; let us now return to our discussion of how humans have reacted to such events over the eons.’
    • ‘The oyamel firs have held their ground on these volcanic hillsides for eons, and Mexico-bound monarchs will spend the winter nowhere else.’
    • ‘If violence was effective, we would have had a peaceful planet eons ago.’
    • ‘He suggested that the age of the Earth might be estimated by comparing the salinity of rivers with the salt content of the oceans, reasoning that the saltiness had built up over the eons.’
    • ‘In short, there is a real-life mystery about what transpired at the Synod of Whitby; the full truth still needs to be teased out from the various clues through the eons.’
    • ‘Then again, women and children have been the targets of violence for eons.’
    • ‘When you see a natural stone formation, you are seeing the result of eons of active degradation and entropy.’
    • ‘In doing so, the court presumably would have to face the question that has puzzled the patent office for decades and philosophers for eons: What makes us human?’
    • ‘And unlike a lot of rock on Earth that has been unrecognizably recycled by volcanic activity over the eons, a lot of lunar material retains records of some of the first impacts.’
    • ‘Consequently, in his view, for eons philosophers have in essence been barking up the wrong tree.’
    number of years, lifetime, duration, length of life
    View synonyms
    1. 1.1Geology Astronomy A unit of time equal to a billion years.
      • ‘It's possible: Astronomers believe that comets and asteroids hitting the Moon eons ago left some water behind.’
      • ‘This mass of molten continent still, however, retains enough homogeneity to be returned more or less as a unit at the mid-ocean ridges eons later as the rock cycle continues.’
    2. 1.2Geology A major division of geological time, subdivided into eras.
      ‘the Precambrian eon’
      • ‘The record has been much deformed, reconstituted, and obliterated during the subsequent Proterozoic and Phanerozoic eons.’
      • ‘Despite our lack of knowledge, or perhaps because of it, researchers have divided the Precambrian into three time periods called eons.’
      • ‘Originally there were only two eons, the Precambrian and the Phanerozoic.’
    3. 1.3Philosophy (in Neoplatonism, Platonism, and Gnosticism) a power existing from eternity; an emanation or phase of the supreme deity.


Mid 17th century: via ecclesiastical Latin from Greek aiōn ‘age’.