Symbiosis (Ancient Greek συμβίωσις symbíōsis: living with, companionship < σύν sýn: together; and βίωσις bíōsis: living) is any type of a close and long-term biological interaction, between two organisms of different species. The two organisms, termed symbionts, can be either in a mutualistic, a commensalistic, or a parasitic relationship. In 1879, Heinrich Anton de Bary defined symbiosis as "the living together of unlike organisms".
