What is the term for a relationship where one organism benefits while the other is harmed?

The term for a relationship where one organism benefits while the other is harmed is parasitism. In a parasitic relationship, the parasite derives benefits such as nutrients or shelter from its host, while the host experiences harm or negative effects, which can range from minor detriment to serious illness or even death. This type of interaction highlights the imbalance of benefits and detriments between the two organisms, with the parasite reliant on the host for survival at the host's expense.

In contrast, the other terms refer to different kinds of ecological interactions. Commensalism describes a relationship in which one organism benefits while the other is neither helped nor harmed. Mutualism involves both organisms benefiting from the relationship, while symbiosis broadly encompasses various types of interactions among species, not limited to just the harmful or beneficial aspects.