In view of the confusion about the use of the term ‘population’ in biology, an analysis has been made of the use of the concept of population in biology. Origin and development, logic and epistemology of the population-concept have been investigated for that purpose. It appears that several concepts of population coexist in biology. The term ‘population’ is used for all these concepts, so it is not amazing that confusion has arisen. This confusion is the more dangerous, since ‘population’ plays (...) an important part in the theory of evolution. A modus has been suggested to diminish this confusion by defining ‘population’ in a very wide sense of the term and by proposing a ‘deme’—terminology to specify the various special concepts of population. (shrink)