Springer and the European Mathematical Society have partnered on this open access Encyclopedia of Mathematics wiki. Based on the high-quality Encyclopaedia of Mathematics published by Kluwer in 2002, this comprehensive graduate-level encyclopedia includes “more than 8,000 entries, illuminating nearly 50,000 notions in mathematics.” Members of the mathematics community are invited to use and contribute to the Encyclopedia; all contributions are reviewed by an editorial board at the European Mathematical Society to maintain the quality of this online reference work.