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  1. Oxford Dictionary

    half-life

    • IPA[ˈhɑːflʌɪf]

    英式

    • n.
      the time taken for the radioactivity of a specified isotope to fall to half its original value；the time required for any specified property (e.g. the concentration of a substance in the body) to decrease by half.

    • noun: half-life, plural noun: half-lifes

    • 釋義

    名詞

    • 1. the time taken for the radioactivity of a specified isotope to fall to half its original value iodine-131 has a half-life of 8.1 days
    • ▪ the time required for any specified property (e.g. the concentration of a substance in the body) to decrease by half.