half-life

or half life, half·life

[ haf-lahyf, hahf- ]

/ ˈhæfˌlaɪf, ˈhɑf- /

noun, plural half-lives [haf-lahyvz, hahf-]. /ˈhæfˌlaɪvz, ˈhɑf-/.

Physics. the time required for one half the atoms of a given amount of a radioactive substance to disintegrate.

Also called biological half-life .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.

Also called half-life period.

Origin of half-life

First recorded in 1905–10; half + life

Words nearby half-life

half-joking, half landing, half-lap joint, half-leather, half-length, half-life, half-light, half-line, half-liter, half-long, half-mad

Dictionary.com UnabridgedBased on the Random House Unabridged Dictionary, © Random House, Inc. 2020

Example sentences from the Web for half-life

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|DAILY BEAST
But the half-life of a piece of hardware is very short these days.
The BlackBerry’s Death Rattle Gets Louder|Daniel Gross|August 12, 2013|DAILY BEAST
And, 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 Saphro
By taking such an attitude to the past we should only fall into the half-will and half-life common to an age of decadence.
Life's Basis and Life's Ideal|Rudolf Eucken

They amused themselves some time with these bright and beautiful creatures, which appear to have but a half-life.
The Swiss Family Robinson; or Adventures in a Desert Island|Johann David Wyss
The half-life must find its mate or, after a few brief days, it dies, leaving its line extinct.
Woman in Modern Society|Earl Barnes
She places herself as his equal—as the other half, without which his half-life cannot be complete.
What a Young Husband Ought to Know|Sylvanus Stall

British Dictionary definitions for half-life

half-life

noun

the time taken for half of the atoms in a radioactive material to undergo decaySymbol: 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

Cultural definitions for half-life

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

Scientists can estimate the age of an object, such as a rock, by carefully measuring the amounts of decayed and undecayed nuclei in the object. Comparing that to the half-life of the nuclei tells when they started to decay and, therefore, how old the object is. (See radioactive dating.)

Medical definitions for half-life

half-life

n.

The time required for half the nuclei of a specific radionuclide or radioactive substance to undergo radioactive decay.physical half-life

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.biological half-life

The time required for the radioactivity of material taken in by or administered to an organism to be reduced to half its initial value by a combination of biological elimination processes and radioactive decay.effective half-life

Scientific definitions for half-life

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.

单词	half-life
释义	half-life or half life, half·life [ haf-lahyf, hahf- ] / ˈhæfˌlaɪf, ˈhɑf- / noun, plural half-lives [haf-lahyvz, hahf-]. /ˈhæfˌlaɪvz, ˈhɑf-/. Physics. the time required for one half the atoms of a given amount of a radioactive substance to disintegrate. Also called biological half-life .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. Also called half-life period. Origin of half-life First recorded in 1905–10; half + life Words nearby half-life half-joking, half landing, half-lap joint, half-leather, half-length, half-life, half-light, half-line, half-liter, half-long, half-mad Dictionary.com UnabridgedBased on the Random House Unabridged Dictionary, © Random House, Inc. 2020 Example sentences from the Web for half-life 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\|DAILY BEAST But the half-life of a piece of hardware is very short these days. The BlackBerry’s Death Rattle Gets Louder\|Daniel Gross\|August 12, 2013\|DAILY BEAST And, 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 Saphro By taking such an attitude to the past we should only fall into the half-will and half-life common to an age of decadence. Life's Basis and Life's Ideal\|Rudolf Eucken They amused themselves some time with these bright and beautiful creatures, which appear to have but a half-life. The Swiss Family Robinson; or Adventures in a Desert Island\|Johann David Wyss The half-life must find its mate or, after a few brief days, it dies, leaving its line extinct. Woman in Modern Society\|Earl Barnes She places herself as his equal—as the other half, without which his half-life cannot be complete. What a Young Husband Ought to Know\|Sylvanus Stall British Dictionary definitions for half-life half-life noun the time taken for half of the atoms in a radioactive material to undergo decaySymbol: 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 Cultural definitions for half-life 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 Scientists can estimate the age of an object, such as a rock, by carefully measuring the amounts of decayed and undecayed nuclei in the object. Comparing that to the half-life of the nuclei tells when they started to decay and, therefore, how old the object is. (See radioactive dating.) 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. Medical definitions for half-life half-life n. The time required for half the nuclei of a specific radionuclide or radioactive substance to undergo radioactive decay.physical half-life 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.biological half-life The time required for the radioactivity of material taken in by or administered to an organism to be reduced to half its initial value by a combination of biological elimination processes and radioactive decay.effective half-life The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company. Scientific definitions for half-life 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.
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