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
Singapore's SkillsFuture provides citizens with credits for continuous education and retraining, acknowledging the shrinking half-life of technical skills.
—
Arafat Kabir, Forbes.com, 4 June 2025
Here’s what to know about caffeine’s half-life, plus the amount of caffeine found in your favorite coffee orders.
—Jillian Kubala, Health, 2 June 2025
In most companies, great ideas have a vanishing half-life: A project team wraps a phase and notices a pattern, or a sales call reveals language that perfectly captures a client’s problem, but then… the idea fades.
—Maggie McGrath, Forbes.com, 23 May 2025
His efforts to blame everyone else for his own failures are sure to have a very short half-life.
—Michael Hiltzik, Los Angeles Times, 20 May 2025
See All Example Sentences for half-life
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Arafat Kabir, Forbes.com, 4 June 2025
Here’s what to know about caffeine’s half-life, plus the amount of caffeine found in your favorite coffee orders.
—Jillian Kubala, Health, 2 June 2025
In most companies, great ideas have a vanishing half-life: A project team wraps a phase and notices a pattern, or a sales call reveals language that perfectly captures a client’s problem, but then… the idea fades.
—Maggie McGrath, Forbes.com, 23 May 2025
His efforts to blame everyone else for his own failures are sure to have a very short half-life.
—Michael Hiltzik, Los Angeles Times, 20 May 2025
See All Example Sentences for half-life
Cite this Entry
“Half-life.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/half-life. Accessed 10 Jun. 2025.
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
The Journal of the American Medical AssociationLove words? Need even more definitions?
Merriam-Webster unabridged
Share