This chapter assesses power, a basic concept of political theory. In its most fundamental sense, power is a dispositional concept that refers to the capacity to affect some feature of the world and the capacity to produce effects with respect to those feature of the world. The concept of power is closely bound in social and political contexts to the concepts of freedom and responsibility. There are different modes of power: power to, power with, power over, and power of. The power of an agent typically depends on the context of power in which they are situated and on the relations in which they stand to other agents within broader social structures. Moreover, exercises of power are always mediated — and, indeed, we often distinguishes forms of social and political power in terms of prominent general media through which they are exercised. The chapter then considers the three-dimensional view of power.