5. These three, length, breadth, and depth, are called dimensions.
6. The forms and dimensions of solids, surfaces, and lines are the objects of geometry.
7. The ends of the edges of the leaf and the corners of the book are points. A point has neither length nor breadth—no magnitude of any kind. But it is in a certain place; that is, it has position; and it is useful in geometry to refer to points, to enable us to indicate exactly particular places or positions.
Hence flow the following definitions:—
8. A point is that which has position, but not magnitude.
A point is named by a letter placed close to it.
9. A line is that which has length without breadth.
A line is named bt letters placed at its ends.
The ends of a line are points, and the intersection (crossing) of one line with another is also a point.
10. A straight line is a line which lies evenly between its ends; that is, which points all in one direction.
The adjoining is a straight line, called AB, as indicating the direction from A to B, or BA, denoting the opposite direction, from B to A.
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11. A straight line is the shortest way between two points. The distance between two points means the straight line between them. Only one straight line can be drawn between two points.
12. The word rectilineal, means "straight-lined."
