Jordan, (Marie Ennemond) Camille (1838-1922)

French mathematician, the greatest exponent of algebra in his day. He concentrated on research in topology, analysis, and particularly group theory, publishing Traité des substitutions et des equations algébriques (1870).

Jordan was born in Lyon and studied engineering at the Ecole Polytechnique in Paris, but it was as a mathematician that he joined its staff in 1873. He also gave lectures at the Collège de France.

Influenced by the work of French mathematician Evariste Galois, Jordan systematically developed the theory of finite groups and arrived at the concept of infinite groups. He also developed three theorems of finiteness.

In topology, Jordan developed an entirely new approach by investigating symmetries in polyhedra from an exclusively combinatorial viewpoint. Moreover, he formulated the proof for the ‘decomposition’ of a plane into two regions by a simple closed curve.

Much of Jordan's later work was concerned with the theory of functions, and he applied the theory of functions of bounded variation to the particular curve that bears his name.

Jordan's work in analysis was published in Cours d'analyse de l'école polytechnique (1882).