# Half-life

From AMS Glossary

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## half-life

The time over which the number of radioactive nuclei of a given species decays exponentially to half its initial value.

Half-lives range from small fractions of a second to billions of years. Half-life is also applied to any exponential decay. That is, if a physical quantity the half-life for this process is τ ln 2, where τ is the mean life.

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