Unipolarity and bipolarity are two different terms used to describe the distribution of power in international relations. Unipolarity refers to a situation where there is only one dominant power in the world, while bipolarity refers to a situation where there are two dominant powers. The key differences between these two concepts are explained below:

1. Distribution of power: In a unipolar world, one country or group of countries dominates the global power structure, while in a bipolar world, two countries or groups of countries hold the majority of the power.

2. Stability: Unipolarity is generally considered to be more stable than bipolarity, as there is only one dominant power that can set the rules and maintain order. In contrast, bipolarity can be more unstable, as the two dominant powers may be in conflict with each other, leading to a potential arms race or even war.

3. Alliances: In a unipolar world, countries may form alliances with the dominant power to gain protection and security. In a bipolar world, countries may align themselves with one of the two dominant powers, and may even be forced to choose sides.

4. Hegemony: In a unipolar world, the dominant power may become a hegemon, exercising significant influence over other countries and shaping the international system to its advantage. In a bipolar world, the two dominant powers may balance each other out, preventing either one from becoming a hegemon.

Overall, the end of bipolarity marked a significant shift in the global power structure, with the United States emerging as the sole superpower. This has had a major impact on international relations, with the United States exerting significant influence over other countries and shaping the global agenda to its advantage. However, the rise of new powers such as China and Russia has challenged this unipolar world order, and the future of international relations remains uncertain.

In political sense Unipolarity means rule or dominance by one country or any one particular area whereas bipolarity means rule or dominance of two country in world affairs. The dominance of USA in today's world in example of unipolarity and the dominance of USA and USSR at the time of cold war is an example of bipolarity.