What is the term used for the rate at which a radioactive substance decays?

The term that describes the rate at which a radioactive substance decays is known as 'half-life.' This concept specifically refers to the amount of time required for half of the radioactive atoms in a sample to decay into a different substance or isotopes. This measurement is crucial because it provides a clear and consistent way to determine how quickly a radioactive material will lose its radioactivity over time.

Half-life is unique for each radioactive isotope, which means it characterizes the rate of decay specific to that isotope. For example, the half-life of carbon-14 is approximately 5,730 years, indicating that after this period, half of a given amount of carbon-14 will have decayed into nitrogen-14.

This term differs from related concepts like decay constant, which provides a more precise mathematical representation of the decay process but does so in a different context. While decay rate might seem like a straightforward description of how quickly a substance decays, it doesn't convey the specific timing that half-life does. Similarly, lifetime is more general and can refer to various contexts beyond just radioactive decay. Therefore, the use of 'half-life' is central to understanding the nature of radioactive decay in a clear and quantifiable manner.