Let $D$ be an integral domain (zero ideal is prime). Then for
every nonzero element $a,b \in D$, we have $<a>\cap <b>\neq 0$.


Now in a general case, let $R$ be a commutative ring with 1, such
that $R$ has no nontrivial idempotent. I am looking for a
general condition (other that $0$ is an irreducible ideal)  for $0$
(the zero ideal) under which $<a>\cap <b>\neq 0$ for all nonzero
element $a,b \in R$.