The mathematical constant π, the ratio of a circle's circumference to its diameter (≈ 3.14159).
円周率は通常πで表され、その値は約3.14159である。
The constant pi is usually denoted by π and its value is approximately 3.14159.
円の面積は半径rを用いてA = πr^2で表される。
The area of a circle with radius r is given by A = πr^2.
小学校で円周率の概念を学んだ。
We learned the concept of pi in elementary school.