to define a unique line in a nontrivial Euclidean space.

The integers modulo 2 form the finite field , the smallest finite field. It has two elements, usually denoted 0 and 1, and addition in corresponds to parity. Thus reduction modulo 2 records the parity of an integer: even integers are congruent to 0 modulo 2, and odd integers are congruent to 1 modulo 2. In algebra, structures of characteristic