Fungi (lat. Mycota) is a kingdom of nature that includes eukaryotic organisms that combine some of the characters of both plants and animals. Fungi is the science of mycology, which is considered a part of botany, as previously fungi were considered to be in the realm of plants.

The concept of fungi as a separate kingdom occurred in science in the 1970’s, although to isolate this kingdom E. Fries in 1831, and Carl Linnaeus expressed doubts, placing mushrooms in the plant kingdom in his “Natural System”. In the 2nd half of the XX century the idea of polyphyletism of mushrooms finally took place. By the end of XX century the data on genetics, cytology and biochemistry have been collected that allowed to divide this group of organisms into several branches not related to each other and allocate them between different kingdoms, leaving in a kingdom of “real”, or proper mushrooms, only one of them. Thus, by the early twenty-first century, the scientific term ‘fungi’ had become ambiguous.

In a close sense, in terms of biological systematics, mushrooms are a taxon, one of the kingdoms of living nature. In the old, more broad sense, the term has lost its taxon meaning, and denotes an ecological and trophic group that unites heterotrophic eukaryotes with osmotrophic type of nutrition. Such organisms customarily continue to be comprehended by mycology.

The biological and ecological diversity of fungi is very great. It is one of the largest and most diverse groups of living organisms and has become an inseparable part of all aquatic and terrestrial ecosystems. According to modern estimates, there are between 100 and 250 thousand, and according to some estimates up to 1.5 million, species of fungi on Earth. As of 2008, 36 classes, 140 orders, 560 families, 8283 usable generic names and 5101 generic synonyms, 97 861 species have been described in the Fungi kingdom.