Algebraic K-theory describes a branch of algebra that centers about two
functors. K0 and K1, which assign to each associative ring ∧ an abelian
group K0∧ or K1∧ respectively. Professor Milnor sets out, in the present
work, to define and study an analogous functor K2, also from associative
rings to abelian groups. Just as functors K0 and K1 are important to
geometric topologists, K2 is now considered to have similar topological
applications. The exposition includes, besides K-theory, a considerable
amount of related arithmetic.