half-life

half-life

(hăf′līf′, häf′-)

n.

1. Physics The time required for half the nuclei in a sample of a specific isotopic species to undergo radioactive decay.

2. Biology

a. The time required for half the quantity of a drug or other substance deposited in a living organism to be metabolized or eliminated by normal biological processes. Also called biological half-life.

b. The time required for the radioactivity of material taken in by a living organism to be reduced to half its initial value by a combination of biological elimination processes and radioactive decay.

American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

half-life

n

1. (General Physics) the time taken for half of the atoms in a radioactive material to undergo decay. Symbol: τ

2. (Biology) 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 and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014

half′-life`

or half′ life`,

n., pl. -lives (-ˌlaɪvz)

1. the time required for one half the atoms of a given amount of a radioactive substance to decay.

2. the time required for the activity of a substance taken into the body to lose one half its initial effectiveness.

[1905–10]

Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.

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® Student Science Dictionary, Second Edition. Copyright © 2014 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

half-life

The time required for the activity of a given radioactive species to decrease to half of its initial value due to radioactive decay. The half-life is a characteristic property of each radioactive species and is independent of its amount or condition. The effective half-life of a given isotope is the time in which the quantity in the body will decrease to half as a result of both radioactive decay and biological elimination.

Dictionary of Military and Associated Terms. US Department of Defense 2005.

half-life

1. A substance which undergoes exponential decay decays by the same ratio in equal intervals of time. The constant ratio is the half-life. The rate of radioactive decay of a substance is defined by its half-life.

2. The time in which half the atoms in a radioactive isotope decay.

Dictionary of Unfamiliar Words by Diagram Group Copyright © 2008 by Diagram Visual Information Limited

Thesaurus

Noun

1.

half-life - the time required for something to fall to half its initial value (in particular, the time for half the atoms in a radioactive substance to disintegrate) half life period, period of time, time period - an amount of time; "a time period of 30 years"; "hastened the period of time of his recovery"; "Picasso's blue period"

Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.

Translations

half-life

[ˈhɑːflaɪf] N (half-lives (pl)) (Phys) → media vida f

Collins Spanish Dictionary - Complete and Unabridged 8th Edition 2005 © William Collins Sons & Co. Ltd. 1971, 1988 © HarperCollins Publishers 1992, 1993, 1996, 1997, 2000, 2003, 2005

half-life

[ˌhɑːfˈlaɪf] n (Phys) → tempo di dimezzamento

Collins Italian Dictionary 1st Edition © HarperCollins Publishers 1995

half-life

1. n. vida media, tiempo requerido para que la mitad de una sustancia ingerida o inyectada en el organismo se elimine por medios naturales;

2. semidesintegración, tiempo requerido por una sustancia radioactiva para perder la mitad de su radioactividad por desintegración.

English-Spanish Medical Dictionary © Farlex 2012

half-life

n vida media

English-Spanish/Spanish-English Medical Dictionary Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.