Heritability: one word, three concepts

The term 'heritability', which evokes the image of transmission from parents to children, is used in biology to characterize the resemblance of related individuals in terms of a given characteristic, and to analyse the genetic and environmental causes of this resemblance. In fact, there are three definitions of heritability and it is important to distinguish among these carefully in order to avoid misinterpretations. Various techniques for measuring associated parameters are linked to these definitions. A rigorous analysis of the assumptions which permit the interpretation of parameter estimates is necessary to avoid false conclusions.