When a quantity decreases by the same factor over equal intervals of time it is said that such quantity is in exponential decay. Exponential decay is modeled using exponential functions with $a>0$ and a base $b$ that is between $0$ and $1.$ In this form, $a$ is the initial amount, the base $b$ is the decay factor, and $t$ usually represents time. Like any other exponential function, $a$ also represents the $y$-intercept. As seen, the closer the base gets to $0,$ the faster the exponential function decays. Since the base $b$ is less than $1,$ it can be written as $1$ minus a positive number $r$ between $0$ and $1.$ This constant $r$ can be interpreted as the rate of decay, in decimal form. A value of $0.12,$ for instance, would mean that the quantity decreases by $12\%$ over every unit of time.