half–life

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noun \ˈhaf-ˌlīf, ˈhäf-\

Definition of half–life

  1. 1 :  the time required for half of something to undergo a process: such asa :  the time required for half of the atoms of a radioactive substance to become disintegratedb :  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. 2 :  a period of usefulness or popularity preceding decline or obsolescence slang usually has a short half–life

First Known Use of half–life

1907


HALF–LIFE Defined for English Language Learners

half-life

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noun

Definition of half–life for English Language Learners

  • : the time it takes for a radioactive substance to lose half its radioactivity


HALF–LIFE Defined for Kids

half–life

play
noun \ˈhaf-ˌlīf, ˈhäf-\

Definition of half–life for Students

plural

half–lives

\-ˌlīvz\
  1. :  the time required for half of the atoms of a radioactive substance to change composition


Medical Dictionary

half–life

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noun \-ˌlīf\

Medical Definition of half–life

  1. :  the time required for half of something to undergo a process: asa:  the time required for half of the atoms of a radioactive substance to become disintegratedb:  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


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