eon

IPA/ˈiːən/
KK[ˈiən]IPA/ˈiːən/

eon — noun

  • eonsingular
  • eonsplural

1. an unimaginably long stretch of time — so long it feels impossible to measure, a

1.名詞B2
釋義

an unimaginably long stretch of time — so long it feels impossible to measure, and the word people reach for when something seems to last forever

例句

Emeka waited for what felt like an eon at the dusty bus stop.

singular: waited… an eon

Soren joked that an eon had slipped by since he last watched a decent film at the Lux.

同義詞
  • age

    suggests a long but somewhat bounded period; 'eon' implies a far greater, almost unmeasurable span

  • eternity

    means endless time, while an eon is vast but still finite

  • forever

    informal and absolute; 'eon' can be plural ('eons') and is more emphatic in writing

反義詞
  • instant

    the shortest imaginable moment

  • moment

    a very brief point in time, the opposite of a vast span

文法句型

an eon

eons

for eons

in eons

用法筆記

Often used in the plural to emphasize extreme length ('eons ago', 'for eons'). The singular 'an eon' appears in phrases like 'wait an eon' or 'an eon passed' when the focus is on a single drawn-out stretch.

常見錯誤

❌Dinosaurs lived during the Jurassic eon.
✅Dinosaurs lived during the Mesozoic Era.
💡An eon is too broad for a single dinosaur period; the Jurassic is an era within an eon.
❌I waited for eon at the shop.
✅I waited for an eon at the shop.
💡When singular, 'eon' needs an article: 'an eon'.

2. a unit of geological and astronomical time equal to one thousand million years —

2.名詞C1
釋義

a unit of geological and astronomical time equal to one thousand million years — in other words, one billion years

例句

Dmitri explained that the Pleiades star cluster was roughly four eons old.

quantified: [number] eons old

Keiko read that the Andromeda galaxy would take another two eons to fully form.

同義詞
  • gigayear

    a technical synonym (1 Ga = 1 billion years), used in specialist scientific writing

文法句型

[number] eons

[number] eons old

[number] eons ago

用法筆記

This is the precise scientific meaning. Distinguish from sense 1 (a vague, immeasurable stretch) and sense 3 (a named division of geological history). Always used with a number or quantity word.

常見錯誤

❌The rocks are an eon old.
✅The rocks are one eon old.
💡For the precise billion-year unit, use a specific number, not the indefinite article.

3. the largest unit of geological time — each eon is made up of several eras and sp

3.名詞C1
釋義

the largest unit of geological time — each eon is made up of several eras and spans hundreds of millions of years. The Archean, Proterozoic, and Phanerozoic are the three most recent ones.

例句

Javier's geology class studied the Archean Eon and its early life forms.

proper noun: the Archean Eon

The Hadean Eon takes its name from the hellish conditions on early Earth, when molten rock covered the planet's entire surface.

同義詞
  • supereon

    an even larger unit; multiple eons grouped together (rarely used outside advanced geology)

文法句型

the [Name] Eon

during the [Name] Eon

用法筆記

Capitalize the name when referring to a specific eon (e.g. 'the Archean Eon') but use lowercase when speaking generally ('the earliest eons'). An eon is larger than an era: eons contain eras, which contain periods.

常見錯誤

❌the archean eon
✅the Archean Eon
💡Formal geological time divisions are capitalized in English.
❌Dinosaurs lived in the Mesozoic Eon.
✅Dinosaurs lived in the Mesozoic Era (within the Phanerozoic Eon).
💡The Mesozoic is an era, not an eon; an eon is the larger unit that contains eras.