单词	half-life
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-life noun as in duration Synonyms & Similar Words Relevance duration lifetime date span time term continuance life life span tenure standing longevity run age tour spell stretch hitch turn
随便看	alpujarra rug alquerque alraun alreadier alreadiest already alright alrighter alrightest alrighty alroot als ALS als ob als obs Alsace Alsace-Lorraine Alsace-Lorrainer alsaces alsatia alsatiae alsatian Alsatian Alsatian clover alsatians

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