第一卷 定义 Definitions 01 /点是没有部分的东西。 Apointis that which has no part. 02 /线是没有宽的长。 Alineis breadthless length. 03 / 线之端是点。 The extremities of a line are points. 04 /直线是其上均匀放置着点的线。 Astraightline is a line which lies evenly with the points on itself. 05 /面是只有长和宽的东西。 Asurfaceis that which has length and breadth only. 06 / 面之端是线。 The extremities of a surface are lines. 07 /平面是其上均匀放置着直线的面。 Aplane surfaceis a surface which lies evenly with the straight lines on itself. 08 /平面角是一个平面上两条线之间的倾斜，它们相交且不在一条直线上。 Aplane angleis the inclination to one another of two lines in a plane which meet one another and do not lie in a straight line. 09 / 且当夹这个角的线是直线时，这个角叫作直线角。 And when the lines containing the angle are straight, the angle is calledrectilineal. 10 / 当一条直线与另一条直线交成的邻角彼此相等时，这些等角中的每一个都是直角，且称这条直线垂直于另一条直线。…