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
This was despite the decay half-life of cesium-137—one of the main contaminating isotopes—being about 30 years.
—
Kate Graham-Shaw, Scientific American, 9 Oct. 2024
The autopsy report also noted that Perry had been receiving ketamine-infusion treatment around the time of his death, but because ketamine has a short half-life, the traces of the substance in his system couldn't have been from those treatment sessions.
—Ryan Coleman, EW.com, 3 Oct. 2024
Due to its half-life of 109 minutes, Flyrcado also can be produced at an offsite pharmacy then delivered to hospitals and imaging centers.
—Kevin Stankiewicz, CNBC, 30 Sep. 2024
Political statements by pop music stars usually have the cultural half-life of a firefly.
—Penny Abeywardena, Forbes, 13 Sep. 2024
See all Example Sentences for half-life 
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Kate Graham-Shaw, Scientific American, 9 Oct. 2024
The autopsy report also noted that Perry had been receiving ketamine-infusion treatment around the time of his death, but because ketamine has a short half-life, the traces of the substance in his system couldn't have been from those treatment sessions.
—Ryan Coleman, EW.com, 3 Oct. 2024
Due to its half-life of 109 minutes, Flyrcado also can be produced at an offsite pharmacy then delivered to hospitals and imaging centers.
—Kevin Stankiewicz, CNBC, 30 Sep. 2024
Political statements by pop music stars usually have the cultural half-life of a firefly.
—Penny Abeywardena, Forbes, 13 Sep. 2024
See all Example Sentences for half-life
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 18 Nov. 2024.
Copy CitationMedical 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—The Journal of the American Medical Association
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