What is the definition of symbiosis?

Symbiosis is a close and often long-term interaction between two different biological species.

Symbiosis is a close and often long-term interaction between two different biological species. In 1877, Albert Bernhard Frank used the word symbiosis to describe the mutualistic relationship in lichens. In 1879, the German mycologist Heinrich Anton de Bary defined it as "the living together of unlike organisms."

source: bing / wikapedia