Contains many of the definitions and theorems from the area of mathematics generally called abstract algebra.
This version of the Encyclopedia of Mathematics is jointly published by Springer and the European Mathematical Society. It is based on the Soviet "Mathematical Encyclopedia" and its English translation (see entry below). It is open access in wiki format, and contains over 8,000 entries. The encyclopedia can be searched or browsed.
Containing 478 articles, this encyclopedia focuses on the fundamental science and mathematics of everyday life. It tries to explain the how and why mathematics works. In addition to the online version, there is a print edition in the Science Library reference collection at QA 10.7 E53 2012 (3 volumes).
An English to Spanish mathematics dictionary.
Based on the Mathematics Subject Classification hierarchy, this is a collection of short articles providing an introduction to each of the disciplines of modern mathematics. There are also links to additional information.
This dictionary contains short discussions of hundreds of terms related to mathematical programming and optimization theory. It may be browsed or searched.
Containing nearly 250,000 sequences, the OEIS is useful for finding information about a particular number sequence. Enter the sequence and the OEIS will provide information about it. There are "hints" for help and an index to browse by name of sequences.
Oxford Reference Online provides access to several mathematics/statistics resources. They may be searched together at the link above or separately at the links below:
PlanetMath is collaborative, online collection of mathematical knowledge. Its main feature is an encyclopedia, but it also includes research papers, books, expositions, and discussion forums.
The Platonic Realms Interactive Mathematics Encyclopedia (PRIME) is a collection of mathematical terms and concepts in areas including algebra, calculus, discrete mathematics, geometry, graph theory, number theory, statistics, and topology. There are also biographies of a few notable mathematicians.
Eric Weisstein's Wolfram MathWorld is a comprehensive and interactive mathematics encyclopedia containing over 13,000 entries along with thousands of figures and hundreds of illustrative animations.