圆的周长 meaning in English

circumference
the perimeter of a circle

the circumference of the circle is 2πr and the time for one revolution is 2πr/v.
圆的周长是2r，转一圈的时间是2rv。
Teacher : what is the perimeter of a circle
师：什么是圆的周长？
Students : the length of the curve making a circle is called the perimeter
生：围成圆的曲线的长度叫做圆的周长。
Teacher : express the way of calculating the perimeter of a circle by letters
师：圆的周长的计算方法，用字母公式表示。
Represents the ratio of the circumference of a circle to its diameter , specified by the constant ,
表示圆的周长与其直径的比值，它通过常数指定。