- - The time taken for fifty per cent of the atoms in a radioactive material to undergo decay
- - First-person shooter game published by Sierra Studios in which players must escape a research facility: Hyph.
- - Period of decay, if .....
- - Radioactive decay measure
- - Physics period
- - Decay concept, in physics
- - Radioactivity figure
- - About 5700 years, for carbon-14
- - 24,110 years, for plutonium 239
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