Exponential decay is a process where a quantity decreases at a rate proportional to its current value. This means that as time goes on, the amount decreases rapidly at first and then slows down. A common example of exponential decay is the way radioactive materials lose their radioactivity over time. The half-life of a substance indicates the time it takes for half of it to decay, illustrating how quickly it diminishes. Another example of exponential decay can be seen in population decline when resources become scarce. As the population decreases, the rate of decline slows down, but the overall trend remains downward. Understanding exponential decay helps us grasp how certain processes, like financial depreciation or disease spread, can change over time.