What characterizes parasitism?

Parasitism is a specific type of symbiotic relationship in which one organism, the parasite, derives benefits at the expense of another organism, the host. This interaction typically results in some form of harm to the host, as the parasite may consume the host's nutrients, steal energy, or weaken its immune system, thereby potentially leading to illness or even death. This harmful aspect is crucial to understanding why this relationship is distinct from others, such as mutualism, where both species benefit, or commensalism, where one benefits without affecting the other. Thus, the essence of parasitism lies in the negative impact it has on the host organism.