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In astronomy, geology, and paleontology, mya is an acronym for 'million years ago'. This abbreviation is commonly used to show the length of time before the present or "B.P." (before AD 1950). Specifically, one mya is equal to 106 years ago.
Mya is traditionally written in lower case (small letters). It is often replaced in scientific literature by a term based on Latin: Ma (megaannum).