1) Concentricity 1) Disk shape 2) Rotundity 3) Roundness 
• (n.) The quality or state of being circular; a circular form.
Cir`cu·lar'i·ty noun [ Late Latin circularitas .] The quality or state of being circular; a circular form. 
[n] - the roundness of a 2-dimensional figure
circularity 1. The roundness of a two-dimensional figure. 2. The quality or fact of being circular in shape. 3. The indirect and complicated nature of something; such as, a method or route. 4. The illogical nature of something; such as, an argument or piece of reasoning.
disk shape noun the roundness of a 2-dimensional figure