I always has the impression that the density of the universe is infinite at the singularity because its just amount of stuff divided by volume and if the distance between stuff is 0 then the volume is 0. So divide by zero and you get infinity. But I have been told by others that dividing by zero is not infinity but undefined. So why not say the density of the universe at the singularity is undefined rather than infinite? Im not assuming the singularity is real just want to understand why this description of the singularity is given.