half-life

noun

ˈhaf-ˌlīf How to pronounce half-life (audio)
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

Examples of half-life in a Sentence

Recent Examples on the Web Tweets in certain languages had a shorter half-life than others, with 49% of Turkish tweets and 42% of Arabic tweets disappearing over the study period. Rob Pegoraro, PCMAG, 20 May 2024 This could be the myth of Blackness itself, that it is never permitted to grow up, to sound too bitter, forever young and inchoate, never atrophying past the dazzling tones of entertainment so that all the world accepts wholeheartedly of Black life is its half-life. Harmony Holiday, Los Angeles Times, 19 Mar. 2024 The report noted that Perry had been receiving ketamine infusion treatment but said the ketamine in his system could not have been from one of those sessions due to its short half-life. Wesley Stenzel, EW.com, 9 Jan. 2024 In addition to the four major PFAS, there are hundreds, if not thousands, of replacement chemicals that have a shorter half-life than the major PFAS. Claire Bugos, Verywell Health, 29 Jan. 2024 For example, just like the mRNAs your body naturally produces, therapeutic mRNAs have a short half-life in cells: about one day. Discover Magazine, 8 Jan. 2024 Key facts about Phenibut HCL include: Short Half-Life: Phenibut HCL has a relatively short half-life of around five hours. The Salt Lake Tribune, 16 Aug. 2023 Uranium has been a hot commodity, and its rally could have a long half-life. Jinjoo Lee, WSJ, 9 Jan. 2024 These levels led the Medical Examiner's Office to conclude that Perry's cause of death was not from his prior infusion therapy —the drug's half-life is just 3 to 4 hours— but rather ketamine that was taken in another manner. Cara Tabachnick, CBS News, 15 Dec. 2023

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'half-life.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

First Known Use

1907, in the meaning defined at sense 1

Time Traveler
The first known use of half-life was in 1907

Dictionary Entries Near half-life

Cite this Entry

“Half-life.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/half-life. Accessed 13 Jun. 2024.

Kids Definition

half-life

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

Medical Definition

half-life

noun
ˈhaf-ˌlīf How to pronounce half-life (audio)
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 daysThe Journal of the American Medical Association
Last Updated: - Updated example sentences
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