Half-life meaning

hăflīf, häf-
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The constant time period required for the disintegration of half of the atoms in a sample of some specific radioactive substance.
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(physics) The time required for half the nuclei in a sample of a specific isotopic species to undergo radioactive decay.
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The time it takes for half of something to decompose, reduce in strength or effectiveness, etc.
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(physics) The time required for half the nuclei in a sample of a specific isotopic species to undergo radioactive decay.
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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.
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The point at which half of the principal has been repaid in a mortgage-backed security. A typical time assumed for half-life is 12 years. If interest rates fall, that time decreases because more homeowners will refinance their mortgages, which will have the effect of paying off the principal more quickly than normal. If interest rates rise and refinancing slows, then the inverse is true.
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Alternative spelling of half-life.
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(physics) The time required for half of the nuclei in a sample of a specific isotope to undergo radioactive decay.
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(chemistry) In a chemical reaction, the time required for the concentration of a reactant to fall from a chosen value to half that value.
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(medicine) The time it takes for a substance (drug, radioactive nuclide, or other) to lose half of its pharmacological, physiologic, or radiological activity.
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The time it takes for an idea or a fashion to lose half of its influential power.
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Origin of half-life