Almost principal ideals and tensor product of hyperlattices

In this paper, by considering the notion of congruences on hyper- lattices we define almost principal ideals on hyperlattices. We investigate some properties and prove some results about them. Also, we define compatible functions on hyperlattices and investigate connection between these functions and almost principal ideals. Then, we define tensor product of two hyperlattices and present several properties such as completeness and distributivity on tensor product of hyperlattices.