Dedekind cut

Etymology
Named after German mathematician (1831–1916), who introduced the concept (although a similar construction was used in Euclid's Elements to define proportional segments).

Noun

 * 1)  Any partition of the set of rational numbers into non-empty sets A and B such that all elements of A are less than all elements of B and A contains no greatest element; intended as a construction of a real number.

Translations

 * Finnish: Dedekindin leikkaus
 * French: coupure de Dedekind
 * Polish: przekrój Dedekinda