lì ǒu / shì / yóu / liǎng gè / dà xiǎo / xiāng děng / fāng xiàng / xiāng fǎn / de / píng xíng lì / zǔ chéng / de

力偶是由两个大小相等、方向相反的平行力组成的。

A couple consists of two parallel forces of equal magnitude and opposite direction.