half-life (h?f?l?f?, 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: ? 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, 2014half?-life` or half? life`, n., pl. -lives (-?la?vz) 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 (h?f?l?f?) 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-lifeThe 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-life1. 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
t-½
t – ½
half-life (h?f?l?f?, 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: ? 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, 2014half?-life` or half? life`, n., pl. -lives (-?la?vz) 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 (h?f?l?f?) 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-lifeThe 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-life1. 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