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

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

. In 1877 Bennett used the word symbiosis (which previously had been used of people living together in community) to describe the mutualistic relationship in lichen

Lichen

Lichens are composite organisms consisting of a symbiotic organism composed of a fungus with a photosynthetic partner , usually either a green alga or cyanobacterium...

s. In 1879, by the German

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 mycologist

Mycology

Mycology is the branch of biology concerned with the study of fungi, including their genetic and biochemical properties, their taxonomy and their use to humans as a source for tinder, medicinals , food and entheogens, as well as their dangers, such as poisoning or...

 Heinrich Anton de Bary, defined it as "the living together of unlike organisms."

The definition of symbiosis is controversial among scientists.