Exponential-Related Distributions
Exponential and related distributions occur in a variety of contexts, such as reliability and communication. As such, a large number of extensions and variations of exponential distributions are frequently used.
Exponential and Related Distributions
ExponentialDistribution — exponentially decreasing PDF
ErlangDistribution — sum of

exponential distributions
Gamma and Related Distributions
GammaDistribution — generalized sum of

exponential distributions