A biocoenosis (biocoenose, biocenose, biotic community, biological community, ecological community), coined by Karl Möbius in 1877, describes the interacting organisms living together in a habitat (biotope). This term is rarely used in English, as this concept has not been popularized in Anglophone countries. Instead, English-speaking scientists usually think about ecosystems or communities.

Descriptors in an ecosystem are:

The geographical extent of a biocenose is limited by the requirement of a more or less uniform species composition.

An ecosystem, as originally defined by Tansley (1935), is a biotic community (or biocoenosis) along with its physical environment (or biotope). In ecological studies, biocoenosis is the emphasis on relationships between species in an area. These relationships are an additional consideration to the interaction of each species with the its physical environment.

Biotic communities vary in size, and larger ones may contain smaller ones. Species interactions are evident in food or feeding relationships. A method of delineating biotic communities is to map the food network to identify which species feed upon which others and then determine the system boundary as the one that can be drawn through the fewest consumption links relative to the number of species within the boundary.