VMS Help SCA, SCA Topics, Glossary, declaration  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Tells the compiler about an object before the compiler uses it.
    This can make the compiler create the object, or it can tell the
    compiler about an object that was created elsewhere. A declaration
    has a position in the source code with both a start and an end,
    and can contain other declarations or references. A declaration
    can be either a primary declaration or an associated declaration.