A number chosen for some reason. When stochaistically or algorithmically computed, random numbers have a relatively flat distribution.
When selected by intelligent processes, random numbers tend to have a much more complex scattering;
often numbers that have personal or cultural value.
Some common randoms are 1 3.14159265358979323846264338327950288419716939937510... 7, 23, 42, 666, 999...