In ecology, commensalism is a class of relationship between two organisms where one organism benefits but the other is neutral (there is no harm or benefit). There are two other types of association: mutualism (where both organisms benefit) and parasitism (one organism benefits and the other one is harmed).

Commensalism derives from the English word commensal, meaning "sharing of food" in human social interaction, which in turn derives from the Latin cum mensa, meaning "sharing a table". Originally, the term was used to describe the use of waste food by second animals, like the carcass eaters that follow hunting animals, but wait until they have finished their meal.

Commensalism is harder to demonstrate than parasitism and mutualism, for it is easier to show a single instance whereby the host is affected, than it is to prove or disprove that possibility. Often, a detailed investigation will show that the host indeed has become affected by the relationship.

An example of commensalism: cattle egrets foraging in fields among cattle or other livestock. As cattle, horses and other livestock graze on the field, they cause movements that stir up various insects. As the insects are stirred up, the cattle egrets following the livestock catch and feed upon them. The egrets benefit from this relationship because the livestock have helped them find their meals, while the livestock are typically unaffected by it.

Sir David Frederick Attenborough ( /ˈætənbərə/) OM, CH, CVO, CBE, FRS, FZS, FSA (born 8 May 1926) is a British broadcaster and naturalist.

His career as the face and voice of natural history programmes has endured for more than 50 years. He is best known for writing and presenting the nine Life series, in conjunction with the BBC Natural History Unit, which collectively form a comprehensive survey of all life on the planet. He is also a former senior manager at the BBC, having served as controller of BBC Two and director of programming for BBC Television in the 1960s and 1970s.

Attenborough is widely considered a national treasure in Britain, although he himself does not care for the term. He is a younger brother of director, producer and actor Richard Attenborough.

Attenborough was born in Isleworth, west London, but grew up in College House on the campus of the University College, Leicester, where his father, Frederick, was principal. He is the middle of three sons (his elder brother, Richard, became an actor and his younger brother, John, an executive at Italian car manufacturer Alfa Romeo). During World War II his parents also adopted two Jewish refugee girls from Europe.