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Banach, Stefan(stĕ`fän bä`näkh), 1892–1945, Polish mathematician. He was educated at the Institute of Technology in Lviv; his doctoral thesis laid the foundations of modern functional analysis, which he continued to work at throughout his life. He also made fundamental contributions to general topology, set theory, the theory of measure and integration, and the general theory of linear spaces, or vector spaces, e.g., Théorie des opérations linéaires (1932). He introduced and developed the concept of complete normed linear spaces, now called Banach spaces.
Born Mar. 30, 1892, in Kraków; died Aug. 31, 1945, in L’vov. Polish mathematician. Professor at the University of L’vov (1924). Dean of the physics and mathematics department of that university (1939).
Banach was one of the founders of contemporary functional analysis. Linear spaces in which linear functionals and operators are most fruitfully studied are named for him. His main work is Theory of Linear Operations, published in Polish (1931), French (1933), and Ukrainian (1948). During the German fascist occupation, Banach was the victim of cruel torment by the fascists. After the liberation of L’vov, he again headed the physics and mathematics department of the University of L’vov.