Kosaku Yosida born on February 7 1909 was brought up in Tokyo. Having majored in Mathematics
at University of Tokyo he was appointed to Assistant at Osaka University in 1933 and promoted
to Associate Professor in 1934. He re ceived the title of Doctor of Science from Osaka
University in 1939. In 1942 he was appointed to Professor at Nagoya University where he worked
very hard with his colleagues to promote and expand the newly established Department of Mathe
matics. He was appointed to Professor at Osaka University in 1953 and then to Professor at
University of Tokyo in 1955. After retiring from University of Tokyo in 1969 he was appointed
to Professor at Kyoto University where he also acted as Director of the Research Institute for
Mathematical Sciences. He retired from Kyoto University in 1972 and worked as Professor at
Gakushuin University until 1979. Yosida acted as President of the Mathematical Society of Japan
as Member of the Science Council of Japan and as Member of the Executive Committee of the
International Mathematical Union. In 1967 he received the Japan Academy Prize and the Imperial
Prize for his famous work on the theory of semigroups and its applications. In 1971 he was
elected Member of the Japan Academy. Yosida went abroad many times to give series of lectures
at mathematical in stitutions and to deliver invited lectures at international mathematical
symposia.
