Points and lines

A point has no length, width or thickness. It merely indi­cates position. To represent a point in geometry we mark

a dot and label it with a capital letter. For example, A or -A would be called "point A".

A line has no width or thickness. It has length and direction. An infi­nite number of straight lines can be drawn through one point.

Since a line extends indefinite in either direction, we must with line segments, or portions in lines. The segment is represented by two capital letters, one placed at each end. The line segment AB or BA is shown in Fig. 2. It can also be represented by small letters. Hence a is line segment a.

A line joins two points. Only one straight line can be drawn between two points. There are three kinds of lines.*straight, curved and broken.

In Fig. 3 AB is a straight line; CD is a curved line; EF is a broken line. Notice that the lines are labeled by capital letters placed at the end of the line.

Lines that extend from left to right as the horizon are called horizontal lines. Examples of horizontal lines are lines on writing paper and all level lines which we find in man-made structures.¹

Note:

¹ man-made structures — постройки и сооружения, соз­данные руками человека