SpringerIranian Journal of Science and Technology (Sciences)1028-627637420131216Approximations in (bi-)hyperideals of Semihypergroups527532179010.22099/ijsts.2013.1790ENR.AmeriSchool of Mathematics, Statistics and Computer Science,
College of Sciences, University of Tehran, P.O. Box 14155-6455, Teheran, IranS.Azizpour ArabiDepartment of Mathematics, University of Mazandaran, Babolsar, IranH.HedayatiDepartment of Mathematics, Babol University of Technology, Babol, IranJournal Article20121126We consider the fundamental relation on a semihypergroup to interpret the lower and upper approximations as subsets of the fundamental semigroup and we give some results in this connection. Also, we introduce the notion of a bi-hyperideal to study the relationship between approximations and bi-hyperideals.http://ijsts.shirazu.ac.ir/article_1790_0e64439a8d53af2ce8801cd97c41d286.pdf