Can anybody define what is meant by the term 'operationalisation', as used in the context of case definitions? The terms is used frequently, yet never explained. It appears to mean something different to merely establishing validity or reliability - the two standard ways of evaluating a case definition. A google search predominantly returns items relating to the need to operationalise ME/CFS case definitions... I'm aware operationalisation was a big issue when psychiatry tried to reform itself through the creation of DSM-III.