Symbiosis, sihm by OH sihs or sihm bee OH sihs, means living together. Any two different species of organisms that live together in a close relationship are symbiotic. In a symbiotic relationship, one member always benefits from the relationship. The other member may also benefit, or it may be harmed or unaffected by the relationship. There are three forms of symbiosis: parasitism, commensalism, and mutualism.