H.S.M. Coxeter was a prominent Canadian mathematician known for his work in geometry, particularly in the study of polytopes and symmetry. Born on February 9, 1907, he made significant contributions to the field of geometric topology and was influential in the development of Coxeter groups, which are important in various areas of mathematics. Coxeter's research extended to higher-dimensional geometry and crystallography, where he explored the properties of regular polytopes and their symmetries. He published numerous papers and books, including the well-known "Regular Polytopes," which remains a key reference in the study of geometric structures. Coxeter passed away on March 31, 2003, leaving a lasting legacy in mathematics.