ABSTRACT
This chapter defines what a group is and gives numerous examples of groups, A group is a non-empty set G with a binary operation. It is important to note that in the definition we do not require that for all a and b, a * b = b * a. If this condition does hold in a group G, we say that G is Abelian or commutative. Some groups are Abelian, or commutative, and some are not. The chapter also presents examples which may seem to the reader to involve natural sets of numbers, permutations, matrices and polynomials, together with natural operations on those sets.
