The its meaning can be better analysed
The doctrine of Separation of Powers is itself a protest against power and its meaning can be better analysed and appreciated, if we drop the reference to ‘powers’ and substitute for it ‘functions’ of the organs or branches of government. “A branch is an organisation of agencies with their personnel. The services they undertake are their functions.” The functions of the government are legislative (rule making), executive (rule application), and judicial (rule adjudication). Accepting this as the criterion of our distinction, the doctrine of Separation of Powers can be restated in the following manner: The activities of government group themselves into three divisions.
These divisions are not a matter of theory, but it is a practical fact associated with the character of the functions themselves. It is one thing to legislate, another to administer, and a third to judge. By assigning each of these functions to different branches of government composed of separate personnel and following their own mode of action, separation is obtained. Such a statement transfers the doctrine from the realm of theory to that of political fact.