What is "unit", when we speak about ∏? The video says that we are taking a 1 unit circle and if we want to find the diameter of this unit circle then we just use the ruler as shown in the video. And now the length of the diameter of this circle is called as PI (∏), which is approximately 3.14 ! And it is constant value with no units!? My question is: 1. What is this "unit" he is talking about? 2. How much is 1 unit? Can this unit be 1 cm in length? 3. How do we measure the length of this 1 unit?