<logic> First-order equational logic consists of quantifier-free terms of ordinary first-order logic, with equality as the only predicate symbol. The model theory of this logic was developed into Universal algebra by Birkhoff et al. [Birkhoff, Gratzer, Cohn]. It was later made into a branch of category theory by Lawvere ("algebraic theories").
Try this search on Wikipedia, OneLook, Google
Nearby terms: EQLog « Eqn « equals « equational logic » Equational Programming Language » Equel » equivalence class