The complex nature of flexibility was demonstrated through the disagreements that exist in the classification and categorization of various types of flexibilities. The concept of flexibility is generally used loosely, but several studies have attempted to describe different types of flexibilities. Besides, current definitions are not precise and the same concept is given different names in different studies. Flexibility types defined in major studies are categorized according to their relationship to the decision making situation that they affect. These classifications, operational flexibility and design flexibility, result from viewing the management problems that occur in flexible manufacturing systems (FMS) as tactical or strategic problems. The machine flexibility refers to the types of operations performed without difficulty in switching from one to the other. The need for an applied focus to flexibility, a departure from theoretical work, was demonstrated. Measures for flexibility were then developed to aid in implementing the new focus to flexibility.