英和和英

略号

bya

1. Abbreviation of billion years ago (A symbol for a unit of measure.)

   Alternative forms: Bya, BYA

   1. (usually) Synonym of Gya (“billion years ago (short scale): 10⁹ years ago”).

      Alternative forms: Bya, BYA

      Coordinate terms: kya, mya

      • 2015, Joyce A. Quinn, Susan L. Woodward, “Introduction”, in Earth's Landscape: An Encyclopedia of the World's Geographic Features, volumes I: A–L, Santa Barbara, CA: ABC-CLIO, →ISBN, page xxxi:

        The first (oldest) unit of time is the Precambrian Supereon, which covers much of Earth's history from its origins roughly 4.55 bya to 545 mya. Very primitive, one-celled life-forms arose as early as 4.0 bya and near the end of the era (570 mya) the oldest known fossils of multi-celled organisms appear.

   2. (uncommon, dated) billion years ago (long scale):10¹² years ago: a trillion years ago (short scale).