Dictionary
half–life
noun \-ˌlīf\
: the time it takes for a radioactive substance to lose half its radioactivity
Full Definition of HALF-LIFE
1
: 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, 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>
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First Known Use of HALF-LIFE
1907
HALF-LIFE Defined for Kids
half–life
noun \ˈhaf-ˌlīf, ˈhäf-\
plural half–lives \-ˌlīvz\
Definition of HALF-LIFE for Kids
: the time required for half of the atoms of a radioactive substance to change composition
Medical Dictionary
half–life
noun \-ˌlīf\
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 days—Journal of the American Medical Association>
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