From abelian group to zero divisor (definitions), and from Artin-Wedderburn theorem to Wedderburn's theorem, this site provides concise explanations of complex concepts in abstract algebra. Provided by Professor John A. Beachy of Northern Illinois University as a companion to two books he has written, it is designed as a handbook for students studying the topic. The site is accessible by chapter (twelve, including integers, polynomials, rings, and Galois Theory, among others), and by alphabetical indices of definitions and theorems. Note that the definitions include many symbols, represented as embedded .gif files.