A set of straight lines or curves used to define a coordinate system; The position of a point on the coordinate axis is uniquely determined by a coordinate value, while the positions of points on other coordinate axes are uniquely determined by a coordinate value, and the values of other coordinates on this axis are zero.

Two intersecting lines used as reference lines in plane analytic geometry

Three straight lines with a common point are the intersection lines of three reference coordinate planes in three-dimensional analytic geometry.

Axis: A line that defines the drawing area of a chart and is used as a reference frame for measurement. The y axis is usually vertical and contains data. The x-axis is usually horizontal and contains classifications.

A spatial coordinate system consisting of three-dimensional orthogonal spatial coordinate axes X, Y and Z can be established in the reference system.