Gegenform
Gegenform is a German term meaning counterform or opposite form. It is used in various technical and artistic contexts to denote a complementary form or the negative mold that enables the creation or delineation of a corresponding object. The word derives from Gegen- meaning against or opposite and Form meaning shape or form.
In moldmaking and sculpture, a Gegenform is typically the counter-mold that closes around a model during casting
Beyond casting, Gegenform is used in design and analysis to refer to an alternative or reciprocal version
See also: mold, counter-mold, negative mold, form in sculpture.