Mutualism is the doctrine that mutual dependence is necessary to social well-being.
Commensalism is an interaction between two organisms living together in more or less intimate association in a relationship in which one benefits and the other is unaffected.
Parasitism is a symbiotic relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has characterized parasites as "predators that eat prey in units of less than one"
