单词	half-lifes
释义	half-life noun ˈhaf-ˌlīf  ˈhäf- 1 : the time required for half of something to undergo a process: such as a : the time required for half of the atoms of a radioactive substance to become disintegrated b : the time required for half the amount of a substance (such as a drug, radioactive tracer, or pesticide) in or introduced into a living system or ecosystem to be eliminated or disintegrated by natural processes 2 : a period of usefulness or popularity preceding decline or obsolescence slang usually has a short half-life Word History First Known Use 1907, in the meaning defined at sense 1 Kids Definition half-life noun ˈhaf-ˌlīf, ˈhäf- plural half-lives -ˌlīvz : the time required for half of the atoms of a radioactive substance to change composition Medical Definition half-life noun ˈhaf-ˌlīf  ˈhȧf- : the time required for half of something to undergo a process: as a : the time required for half of the atoms of a radioactive substance to become disintegrated b : the time required for half the amount of a substance (as a drug or radioactive tracer) in or introduced into a living system or ecosystem to be eliminated or disintegrated by natural processes the serum half-life is about 2 days Journal of the American Medical Association half-lifes noun variants or half-lives plural of half-life as in lifetimes Synonyms & Similar Words Relevance lifetimes durations runs times dates spans terms continuances ages lives tenures life spans longevities standings tours hitches spells stretches turns
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