codomain

noun2

1. •
   The target set into which a function is formally defined to map elements of its domain; the set denoted Y in the notation f : X → Y.

   • Definition 2.5. A function is onto if each element of the codomain has at least one element of the domain assigned to it. In other words, a function is onto if the range equals the codomain. — 1994
2. •
   The set B.