圆心

tóng xīn yuán de yuán xīn bì dìng chóng hé

同心圆的圆心必定重合。

The centers of concentric circles must coincide.

tā zǒu dào yuán xīn

她走到圆心。

She walked to the center of the circle.

yuán de zhí jìng bì xiāng jiāo yú yuán xīn

圆的直径必相交于圆心。

The diameter of a circle must go through the center.