The term for the time it takes for half of a substance to decay is “half-life.” This concept is commonly used in nuclear physics and chemistry to describe the decay of radioactive isotopes and other unstable materials. During each half-life period, half of the original quantity of the substance will transform into a different element or isotope. Half-life can vary significantly among different substances—ranging from fractions of a second to millions of years. Understanding half-life is crucial for applications in radiometric dating, nuclear medicine, and environmental science as it helps determine the longevity and stability of radioactive materials.