Zipf-Mandelbrot law
The Zipf-Mandelbrot law (also known as the Pareto-Zipf law) is a power-law distribution on ranked data, named after the Harvard linguistic professor George Kingsley Zipf (1902-1950) who suggested regularity in texts, and the mathematician Benoit Mandelbrot (born November 20, 1924), who generalized it.The distribution of words ranked by their frequency in a random corpus of text is generally a power-law distribution, known as Zipf's law.
If one plots the frequency rank of words contained in a large corpus of text data versus the number of occurrences or actual frequencies, one obtains a power-law distribution, with exponent close to one (but see Gelbukh and Sidoro 2001).