资料来源 : Free On-Line Dictionary of Computing

infinite set
     
         A set with an infinite number of elements.
        There are several possible definitions, e.g.
     
        (i) ("Dedekind infinite") A set X is infinite if there exists
        a {bijection} (one-to-one mapping) between X and some proper
        subset of X.
     
        (ii) A set X is infinite if there exists an {injection} from N
        (the set of {natural number}s) to X.
     
        In the presence of the {Axiom of Choice} all such definitions
        are equivalent.
     
        (1995-03-27)