The concepts of process directionality and ill-conditionedness are studied. The definition of these concepts commonly used in the literature is shown to be insufficient, due to the wide range of different applications connected to directionality studied in the field of process control. The commonly used definition does not provide a general concept, which leads to a state where directionality is used in a very problem-specific way. With the aim of achieving a general concept, a refinement of the definition of process directionality is proposed. The refinement divides the concept of directionality into two parts, which are connected to stability and performance aspects, respectively. The refinement of the definition clarifies the connection between control difficulties and directionality, and it also clarifies the scaling choice when modeling a process with respect to directionality analysis.