Meaning & use
Bya
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A scientific abbreviation meaning "billion years ago," used chiefly in geology, astronomy, and paleontology to date events in Earth's or the universe's history.
See it in a sentence
The oldest known rocks on Earth formed roughly 4 bya.
Scientists estimate the Milky Way began forming around 13.6 bya.
A note on using this word
"Bya" is used alongside similar abbreviations like "mya," meaning million years ago, in scientific writing about deep time.
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