Definition:Group

Definition
A group is a semigroup with an identity (that is, a monoid) in which every element has an inverse.

Group Axioms
The properties that define a group are sufficiently important that they are often separated from their use in defining semigroups, monoids, and so on, and given recognition in their own right.

The notation $\struct {G, \circ}$ is used to represent a group whose underlying set is $G$ and whose operation is $\circ$.

Multiplicative Notation
When discussing a general group with a general group product, it is customary to dispense with a symbol for this operation and merely concatenate the elements to indicate the product.

Compare with additive notation.

Also denoted as
Some sources use the notation $\gen {G, \circ}$ for $\struct {G, \circ}$.

Also see

 * Definition:Left Group Axioms
 * Definition:Right Group Axioms


 * Equivalence of Axiom Schemata for Groups


 * Definition:Abelian Group