As of 1 April 2026, the PSJD database will become an archive and will no longer accept new data. Current publications from Polish scientific journals are available through the Library of Science: https://bibliotekanauki.pl
The article is devoted to the evolution of concept of a number in XVIII–XIX c. Ch. Méray’s, H. Heine’s, R. Dedekind`s, G. Cantor’s and K. Weierstrass`s constructions of a number are considered. Only original sources were used.