hear it again1 : the living together in close association of two different kinds of organisms (as a fungus and an alga making up a lichen) especially when such a relationship is of benefit to both.
2 : a cooperative relationship (as between two persons or groups).
Example sentence:
In some forms of symbiosis—such as that of termites and the protozoans that live inside of them and digest the wood eaten by the termites—neither species can live without the other.
Etymology:
The Greek ancestors of "symbiosis" are "bios," meaning "life," and "syn," meaning "together." "Bios" is also the ancestor of our combining form "bi-" or "bio-." It can be found in many English words that have some connection to life, such as "biography," meaning "a history of a person's life," and "biosphere," meaning "the part of the world in which life can exist." If you look for other related words, be sure you don't confuse the Greek "bi-, bio-," with the Latin prefix "bi-," which means "two."