Which of the following best describes half-life?

Half-life is defined as the time required for one-half of a substance to decay. This concept is particularly prevalent in the fields of nuclear physics and chemistry, where it refers to the time it takes for a radioactive isotope to reduce to half of its initial quantity through the process of radioactive decay. This definition underscores the concept of decay as an exponential process, where the substance decreases by half at consistent intervals of time.

The other options do not accurately capture the essence of half-life. For instance, describing half-life as the time it takes for a substance to become stable does not reflect the gradual process of decay; rather, stability may refer to a state achieved in different contexts. Similarly, stating that it is the period for a complete reaction to occur or the time necessary for the complete transformation of elements misinterprets the nature of half-life, which specifically involves the decay of a portion of a substance rather than the entirety. Thus, the option stating that half-life is the time required for one-half of a substance to decay is the most accurate representation of this concept.