Abstract

We show that the class of contact join-semilattices introduced by Ivanova (Contact join-semilattices. Stud Log 2022;110:1219–41) is not finitely axiomatizable. On the other hand, a simple finite axiomatization exists for the class of those join-semilattices with a weak contact relation, which can be embedded into the reduct of a weak contact Boolean algebra (equivalently, distributive lattice).