Groups of order 2
This article gives information about, and links to more details on, groups of order 2
See pages on algebraic structures of order 2| See pages on groups of a particular order
There is, up to isomorphism, a unique group of order 2, namely cyclic group:Z2. This can be proved in many ways, including simply listing possible multiplication tables, but it also follows from the fact that 2 is a prime number and there is a unique isomorphism class of group of prime order, namely that of the cyclic group of prime order.