A key in ProbabilityDistribution objects and an option for discreteProbabilityDistribution and continuousProbabilityDistribution for setting the probability density/mass function to be used by density.
The object DensityFunction is a symbol.
The source of this document is in /__w/M2/M2/macaulay2-1.26.05+ds/M2/Macaulay2/packages/Probability.m2:555:0.