Commensalism is an interaction between individuals of different species that benefits one species while having a neutral effect on the other. The term is used somewhat differently in different fields. In the original definition, based on the work of the Belgian parasitologist and palaeontologist Pierre-Joseph van Beneden, a commensal is an organism that depends on another species for food by sharing its food resources but, unlike a parasite, does not harm it. In close association, the organism providing the food is called the host and the organism benefiting from it is the commensal. The host experiences neither benefit nor harm. The commensal alone benefits from the association and is usually dependent on the host. It mainly feeds on waste products or surplus food from the host without removing substances essential to the host’s survival.

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