Erdős number

Etymology
.

Noun

 * 1)  A number describing the degree of collaboration between a mathematician and Paul Erdős, defined such that a mathematician who has written a paper with Erdős has an Erdős number of 1, a mathematician who has written a paper with somebody having an Erdős number of 1 has an Erdős number of two, and so on.

Translations

 * German: Erdős-Zahl
 * Hungarian:
 * Portuguese: número de Erdös
 * Romanian: număr Erdős
 * Russian: число́ Э́рдёша
 * Swedish: