Authority involves the exercise of legitimate power over the people. Without legitimacy authority takes the form of power or even force. Legitimacy denotes the rightfulness or justness of authority and secures for it a high level of obedience and respect.
The term legitimacy has been derived from the Latin word Legitimare which means to declare lawful. It broadly means rightfulness or justness.
Before defining legitimacy we must understand, as Blondel points out, that the legitimacy of the political system as a whole is intertwined with legitimacy of the groups that exist in the polity. Particularly the legitimacy of the leadership constitutes a determinant of the legitimacy of the Political System.
“Legitimacy is the extent to which the population accepts naturally, without questioning the organisation to which it belongs.” “The broader the area of agreement of acceptance, the more legitimate is the organisation.” —Jean Blondel
In other words Legitimacy means the extent to which people accept as rightful the leadership and the values made and enforced by the political system. It depends, among other factors, upon the legitimacy of the groups, particularly the group which holds power at a particular time.
“Legitimacy includes the capacity to produce and maintain a belief that existing political institutions or forms are the most appropriate for the society.” —S.M. Lipset
“Belief that the structures, procedures, acts, decisions, policies, officials or leaders of government possess the quality or ‘rightness’, propriety or moral goodness and should be accepted because of this quality irrespective of the specified content of the particular act in question is what we mean by legitimacy.” —Robert Dahl
“Legitimacy is that principle which indicates the acceptance on the part of the public of the occupancy of a political office by a particular person, or the exercise of power by a person or group, on the grounds that occupancy or exercise of powers is in accordance with some generally accepted principles and procedures of conformant of authority.” —J.C. Piano and R.E. Riggs
In simple words, Legitimacy is the quality of a political system, particularly its government, to produce and maintain a belief that the existing structures, institutions and values being made and implemented by it are most appropriate for the society.
It is the quality that makes the people obey, support and respect the decisions of the political system and the authority holders. Legitimacy means the quality of enjoying the just and rightful power/authority to rule and command. Legitimacy means belief in the justness or rightfulness of a regime or a system of rule.