A description of a group in terms of generators and relations. For example, 〈x | xn = e〉 is a group with a single generator x of order n and so is the cyclic group of order n. The dihedral group D2n has the presentation
Words in the generators are equal if and only the relations can be used to show this. Formally, the presentation defines a group as the quotient group of the free group on the set of generators by the normal subgroup generated by the relations.