Randomness should not be confused with practical unpredictability, which is a related idea in ordinary usage. Some mathematical systems, for example, could be seen as random; however they are actually unpredictable. This is due to sensitive dependence on initial conditions (see chaos theory). Many random phenomena may exhibit organized features at some levels.

When working with probability, it is often useful to run experiments such as computational simulations. Many programming languages have the ability to generate pseudo-random numbers which are effectively distributed according to the standard uniform distribution.