WordNet (r) 3.0 (2006):

range of a function
    n 1: (mathematics) the set of values of the dependent variable
         for which a function is defined; "the image of f(x) = x^2
         is the set of all non-negative real numbers if the domain
         of the function is the set of all real numbers" [syn:
         image, range, range of a function]