Exponential Decay:A process where a quantity decreases at a rate proportional to its current value, often modeled with the function $y = y_0 e^{-kt}$.
Half-Life: The time required for half of a given amount of a radioactive substance to decay.
Logarithmic Function:$y = \log_b(x)$ is the inverse function of an exponential function; it determines how many times one number must be multiplied by itself to obtain another number.