The partner organisms are called the symbiont and the host . Commensalism is a symbiotic relationship between two partners, the host and the symbiont. One partner, the host, is not harmed. The other partner, the symbiont, benefits greatly. Mutualism is a symbiotic relationship in which both the symbiont and the host benefit.
Parasitism is a symbiotic relationship in which the symbiont benefits at the expense of the host.
In parasitism the host is harmed and the symbiont benefits. In commensalism , one partner, the symbiont, benefits, and the other partner, the host, is not harmed in a major way. Mutualism is a form of symbiosis in which both the symbiont and the host benefit from the relationship. Many reef organisms exhibit cleaning symbiosis , a symbiotic relationship in which one partner cleans the other. Since both partners benefit from the relationship, this form of symbiosis is called mutualism.