“In ecology, commensalism is a class of relationship between two organisms where one benefits and the other is not significantly harmed or benefited. The term derives from the English word commensal, meaning "sharing of food" in human social interaction, which in turn derives from the Latin com mensa, meaning "sharing a table". It is contrasted with mutualism, in which both organisms benefit, and parasitism, in which one organism gains at the other's expense.”
http://en.wikipedia.org/wiki/Commensalism
