A random variable is one whose value is unknown or a function that assigns values to each of an experiment’s outcomes. A random variable can be discrete or continuous.

Robin J. Evans, Thomas S. Richardson, MARKOVIAN ACYCLIC DIRECTED MIXED GRAPHS FOR DISCRETE DATA, The Annals of Statistics, Vol. 42, No. 4 (August 2014), pp. 1452-1482 ...

For example, stock prices are discrete random variables, because they can only take on certain values, such as $10.00, $10.01 and $10.02 and not $10.005, since stocks have a minimum tick size of ...

John Aitchison, On the Distribution of a Positive Random Variable Having a Discrete Probability Mass at the Origin, Journal of the American Statistical Association, Vol. 50, No. 271 (Sep., 1955), pp.