πd = C.
The ratio of circumference to diameter is a fixed constant. No matter how large or how small the circle, the ratio of its circumference to diameter is always just a little over 3. 3.14 to be more accurate, sometimes approximated by 22/7.
To be more precise, the value is: 3.1415926535... and never repeats or terminates. The letter used to represent this value is the Greek letter "pi" which is pronounced "pie."
