Symbiosis (from Greek συμβίωσις "living together", from σύν "together" and βίωσις "living")[2] is a close and often long-term interaction between two different biological species. In 1877 Albert Bernhard Frank used the word symbiosis (which previously had been used to depict people living together in community) to describe the m u t u a l i s t i c relationship in lichens.[3] In 1879, the German mycologist H e i n r i c h Anton d e B a r y defined it as "the living together of unlike organisms."