In mathematics, numbers can be represented by points on a straight line, which is called the number axis and meets the following requirements:

1, take any point on a straight line to represent the number 0, and this point is called the origin.

2. Generally speaking, from the origin to the right (or upward) is the positive direction, and from the origin to the left (or downward) is the negative direction.

3. Choose an appropriate length as the unit length, which is expressed as-1 and -2 in turn from the origin to the right in a straight line in a similar way.

Mathematically, the number axis is a one-dimensional figure, and integers are evenly distributed on a line as special points. The number axis is a straight line that defines the origin, direction and unit length. The origin, direction and unit length are called the number axis. It is usually used to help teach simple addition or subtraction (especially when there are negative numbers in the operation).

The role of the number axis:

1, the number axis can visually represent numbers, and the points on the horizontal number axis correspond to real numbers one by one, that is, each real number can be represented by a point on the number axis.

2. Compare the sizes of real numbers, with 0 as the center, and the number on the right is greater than the number on the left.

3. The imaginary number can also be represented by the vertical number axis perpendicular to the horizontal number axis and with the same origin, thus forming a complex plane with the horizontal number axis.

4. Plane rectangular coordinate system can be composed of two mutually perpendicular number axes with the same origin. Three mutually perpendicular number axes with the same origin can form a spatial rectangular coordinate system to determine the position of an object.

The number axis has the completeness of numbers, which can represent both rational and irrational numbers (collectively called real numbers) and imaginary numbers. At the same time, a coordinate system can be established to form a relatively strict digital system.