Medical Dictionary


noun \-ˌlīf\

Medical Definition of half–life

  1. :  the time required for half of something to undergo a process: asa:  the time required for half of the atoms of a radioactive substance to become disintegratedb:  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

Learn More about half–life

  1. Spanish Central: Translation of half–life

Seen and Heard

What made you want to look up half–life? Please tell us where you read or heard it (including the quote, if possible).


a rounded knoll or a ridge of ice

Get Word of the Day daily email!