ABSTRACT
In this chapter we begin our investigation of hyperidentities and hypervari eties. Hyperidentities are formally the same as identities, but are considered in a higher-order way. Just as we use identities to classify algebras into model classes called varieties, we can examine what identities a variety might satisfy, and use such identities to classify varieties too into collections. To emphasize that this is one level higher than individual algebras and their identities, the new identities for varieties are called hyperidentities, and their model classes are called hypervarieties.
