In a symbiotic relationship where one organism benefits at the expense of the host, what is this called?

In a symbiotic relationship where one organism benefits at the expense of the host, this relationship is called parasitism. In parasitism, the parasite derives nutrients or some other benefit from the host, which usually suffers negative effects as a result. For example, tapeworms in the intestines of animals obtain food while harming their hosts by depriving them of nutrients. This relationship highlights the imbalance in benefits, where the parasite thrives at the cost of the host's health or well-being.

In contrast, mutualism refers to a relationship where both organisms benefit, commensalism describes a situation where one organism benefits while the other is unaffected, and neutralism involves two organisms coexisting without affecting each other. Each of these represents a different type of interaction in ecology, with parasitism being distinctly characterized by the harm it inflicts on the host.