Meaning of half-life


Pronunciation: (haf'līf", häf'-), [key]
— pl. -lives
  1. the time required for one half the atoms of a given amount of a radioactive substance to disintegrate.
  2. the time required for the activity of a substance taken into the body to lose one half its initial effectiveness.
  3. a brief period during which something flourishes before dying out.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.