Mathematician, born in Wrocław, Poland (formerly Breslau, Germany). He studied at Leipzig and Berlin, and taught at Leipzig (1896--1910). In 1910 he moved to Bonn, where he stayed until, as a Jew, he was forced by the Nazis to resign his chair in 1935; ultimately he committed suicide with his family, to avoid the concentration camps. He is regarded as the founder of point set topology, and his book Grundzüge der Mengenlehre (1914) introduced the basic concepts of topological spaces and metric spaces which have since become part of the standard equipment of analysis and topology. His work on set theory continued that of Cantor and Zermelo.