Zipf's law

Etymology
. After (1902–1950), American linguist. From the observed distribution of a word's frequency of occurrence against its rank of occurrence, discovered in Zipf's research, as a graph of logarithm of frequency against logarithm of ranking resulting in a straight line with -1 slope.

Proper noun

 * 1) The fact that many types of data studied in the physical and social sciences can be approximated with a Zipfian distribution.