the gamma distribution is often used (for example, in neuroscience for spiking rates for the refactory period) to capture the case where you do not wish to give

the gamma distribution is often used (for example, in neuroscience for spiking rates for the refactory period) to capture the case where you do not wish to give support to zero plus some short period after zero. the exponential distribution is a kind of gamma distribution: Gamma(1,lambda) = Exp(lambda)