Cóng / zhíxiàn / wài / yì / diǎn / xiàng / zhè / tiáo / zhíxiàn / zuò / chuíxiàn / chuíxiàn / zú / jiù / shì / chuí / zú

从直线外一点向这条直线作垂线，垂线足就是垂足。

From a point outside a line, draw a perpendicular to it; the foot of the perpendicular is the projection point.