Gya
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In [[astronomy]], [[geology]], and [[paleontology]], '''Gya''' (for [[giga]] years ago) is often used as an [[Units of measurement|unit]] of [[time]] to denote length of time before the present. Specifically, one Gya is equal to 10<SUP>9</SUP> [[year]]s ago.
A unit identical to Gya is [[bya]] (for "[[1000000000 (number)|billion]] years ago"), which may be in more widespread use. However, some scientists prefer Gya because it uses the [[SI]] prefix [[giga-]] and thus avoids confusion over whether the short-scale ([[American English|American]]) billion (10<SUP>9</SUP>) or long-scale ([[British English|British]]) billion (10<SUP>12</SUP>) is meant, as well as avoiding preference for one of the two definitions of billion over the other.
In some scientific literature, the term Gya has been replaced by '''[[Gigaannum|Ga]]''' ([[Giga-annum]]).
== See also ==
* [[annum]]
* [[Before Present]]
* [[bya]]
* [[mya (unit)]]
[[Category:Units of time]]
[[hu:Gya]]