Book 1
DEFINITIONS.
1
1
A point is that which has no part.
2
2
A line is breadthless length.
3
3
The extremities of a line are points.
4
4
A straight line is a line which lies evenly with the points on itself.
5
5
A surface is that which has length and breadth only.
6
6
The extremities of a surface are lines.
7
7
A plane surface is a surface which lies evenly with the straight lines on itself.
8
8
A plane angle is the inclination to one another of two lines in a plane which meet one another and do not lie in a straight line.
9
9
And when the lines containing the angle are straight, the angle is called rectilineal.
10
