half-life
or half life, half·life
Physics. the time required for one half the atoms of a given amount of a radioactive substance to disintegrate.
Also called bi·o·log·i·cal half-life [bahy uh-loj i kuhl haf-lahyf] /ˈbaɪ əˈlɒdʒ ɪ kəl ˈhæfˌlaɪf/ .Pharmacology. the time required for the activity of a substance taken into the body to lose one half its initial effectiveness.
Informal. a brief period during which something flourishes before dying out.
Origin of half-life
1- Also called half-life pe·ri·od [haf-lahyf peer-ee-uhd] /ˈhæfˌlaɪf ˌpɪər i əd/ .
Words Nearby half-life
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2024
How to use half-life in a sentence
The half-life of a piece of technology these days is very short.
ecoATM offers consumers a new way to sell used cell phones and electronic devices | Sarah Langs | September 1, 2013 | THE DAILY BEASTBut the half-life of a piece of hardware is very short these days.
Radiation dissipates over time with every isotopic half-life.
Radioactive Tuna Won’t Kill You—but Should We Be Concerned About Mercury? | Daniel Stone | May 30, 2012 | THE DAILY BEASTIt was a small picture, half life-size, and set in an oval frame of black walnut.
Theo | Mrs. Frances Hodgson BurnettA very beautiful marble group, half life-size, stood in one corner, and gave an air of brightness to the whole room.
Dr. Jolliffe's Boys | Lewis Hough
Now the old problem of half-life is taking its toll, and we cant even hope to keep up with the birth rate any more.
They Also Serve | Donald E. WestlakeAnd, finally, Moglaut had warned that the compact power unit pocketed on the left breast had a half-life of only thirteen years.
Zero Data | Charles SaphroThen he knew all hope was over, and the mad passion went out of him, and his arms dropped to his sides as if half life had fled.
Beyond The Rocks | Elinor Glyn
British Dictionary definitions for half-life
the time taken for half of the atoms in a radioactive material to undergo decay: Symbol: τ
the time required for half of a quantity of radioactive material absorbed by a living tissue or organism to be naturally eliminated (biological half-life) or removed by both elimination and decay (effective half-life)
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Scientific definitions for half-life
[ hăf′līf′ ]
The average time needed for half the nuclei in a sample of a radioactive substance to undergo radioactive decay. The half-life of a substance does not equal half of its full duration of radioactivity. For example, if one starts with 100 grams of radium 229, whose half-life is 4 minutes, then after 4 minutes only 50 grams of radium will be left in the sample, after 8 minutes 25 grams will be left, after 12 minutes 12.5 grams will be left, and so on.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Cultural definitions for half-life
In physics, a fixed time required for half the radioactive nuclei in a substance to decay. Half-lives of radioactive substances can range from fractions of a second to billions of years, and they are always the same for a given nucleus, regardless of temperature or other conditions. If an object contains a pound of a radioactive substance with a half-life of fifty years, at the end of that time there will be half a pound of the radioactive substance left undecayed in the object. After another fifty years, a quarter-pound will be left undecayed, and so on.
Notes for half-life
The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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