Some distributions are exponential families only if some of their parameters are held fixed. The family of Pareto distributions with a fixed minimum bound "x"m form an exponential family. The families of binomial and multinomial distributions with fixed number of trials "n" but unknown probability parameter(s) are exponential families. The family of negative binomial distributions with fixed number of failures (a.k.a. stopping-time parameter) "r" is an exponential family. However, when any of the above-mentioned fixed parameters are allowed to vary, the resulting family is not an exponential family.