As noted in (the editorial comments to) Algebraic systems, quasi-variety of, the quasi-identities (cf. Quasi-identity) defining a quasi-variety are usually called Horn sentences. Correspondingly, a quasi-variety is also known as a universal Horn class; it is also called a quasi-primitive class.
|[a1]||P.M. Cohn, "Universal algebra" , Reidel (1981) pp. 235|
Quasi-variety. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Quasi-variety&oldid=16055