What is the definition of radioactive half-life?

Radioactive half-life is a fundamental concept in the study of radioactive decay, referring specifically to the time required for half of the radioactive nuclei in a sample to decay. This completes the cycle of disintegration for a quantity of material, meaning that after one half-life has passed, 50% of the original amount of the radioactive substance will have transformed into a different element or isotope, leaving only 50% of the original substance remaining.

Understanding this concept is essential for various applications, including nuclear medicine, radiometric dating, and understanding the safety and handling of radioactive materials. The definition emphasizes that the focus is solely on half of the material disintegrating, not a different fraction, which is why the other options do not hold true. Terms like one-third, one-fourth, or one and one-half do not accurately represent the specific characteristic that defines radioactive decay, making them incorrect in this context.