half-life

noun
\ ˈhaf-ˌlīf How to pronounce half-life (audio) , ˈhäf- \

Definition of half-life

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

First Known Use of half-life

1907, in the meaning defined at sense 1

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The first known use of half-life was in 1907

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Cite this Entry

“Half-life.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/half-life. Accessed 2 Mar. 2021.

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More Definitions for half-life

half-life

noun

English Language Learners Definition of half-life

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

half-life

noun
\ ˈhaf-ˌlīf, ˈhäf- \
plural half-lives\ -​ˌlīvz \

Kids Definition of half-life

: the time required for half of the atoms of a radioactive substance to change composition

half-life

noun
\ -ˌlīf How to pronounce half-life (audio) \

Medical Definition of half-life

: 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 daysJournal of the American Medical Association

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