Vladimir Voevodsky revolutionized algebraic geometry and is best known for developing the new field of "motivic homotopy theory." His contributions to computer formalization of proofs and the foundations of mathematics also made an immense impact.
Algebraic geometry is the study of geometric aspects of systems of polynomial equations, such as the equation x2 + y2 = 1, which yields a circle when x and y are real numbers, and something sharing the topological flavour of a circle when x and y are more abstract sorts of numbers. Voevodsky joins a line of great mathematicians, including Bernhard Riemann and Alexander Grothendieck, who built algebraic geometry into a deep and powerful science over the past two centuries. He died in September, aged 51, at his home in Princeton, New Jersey.