https://mathigon.org/course/circles/introduction

The diameter is the distance between two opposite points on a circle. It goes through its center, and its length is twice the radius.

 

but  in  chinese 

直径 表示圆上两个相对的点的距离。它通过圆心,长度为半径的一半。

it means

The diameter is the distance between two opposite points on a circle. It goes through its center, and its length is half

i think its wrong