# Coordinate axis

**Coordinate axes** are highlighted lines that provide the reference for position information in area or space. Usually these are straight, intersecting lines, as in the Cartesian coordinate system , which together form the **axis cross** . This is used for flat objects

- the abscissa axis (x-axis), the horizontal (horizontal) coordinate axis, and
- the ordinate axis (y-axis), the vertical (perpendicular) coordinate axis on it.

In the case of spatial objects there is also

- the application axis (z-axis), the axis perpendicular to the other two axes.

Note: The term coordinate axis does not apply to circles as reference lines, as used by our geographic coordinate system for "longitude" and "latitude".

Two coordinate axes:

*y*over*x*with scale division (according to DIN 461 )

The axes indicate the qualitative or quantitative framework in which a functional relationship between two variables is to be illustrated in a preferably flat, right-angled coordinate system . A third variable can be taken into account by parallel projection or as a parameter in a family of curves or in a family of characteristics .

The *axis labeling* with the sizes shown serves as a first orientation . The position of the intersection point of the two coordinate axes helps for further orientation, which is often, but not necessarily, the origin of the coordinate system at which both coordinates assume the value zero. Due to different options, this prominent point should always be labeled on both axes. The names of the rooms divided by the three levels are called octants .