What does the term "half-life" refer to in nuclear physics?

The term "half-life" in nuclear physics specifically refers to the time required for the activity of a radioactive source to decrease to half its initial value. Radioactive decay is a random process, and the half-life is a statistical measure that indicates how quickly a radioactive substance disintegrates over time. After one half-life, half of the original quantity of radioactive atoms will have decayed, leading to a reduction in the emitted radiation or activity.

Understanding half-life is crucial in various fields such as medicine, archaeology (for carbon dating), and nuclear power, as it helps predict how long a radioactive substance will remain hazardous or effective. In contrast, characteristics such as the time taken for a substance to completely decay or to double its mass do not accurately define half-life, nor does it pertain to achieving stable nuclear reactions.