# Definition:Axis/Z-Axis/Right-Hand Rule

< Definition:Axis | Z-Axis

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## Definition

The usual convention for the orientation of the $z$-axis is that of the right-hand rule:

Let the coordinate axes be oriented as follows:

Then the $z$-axis increases from **below** to **above**.

If the $x$-axis and $y$-axis are aligned with a piece of paper or a screen aligned perpendicular to the line of sight, this translates into the following orientation:

Then the $z$-axis increases from **behind** to **in front** (that is, from **further away** to **closer in**).

## Sources

- 2008: Ian Stewart:
*Taming the Infinite*... (previous) ... (next): Chapter $6$: Curves and Coordinates: Descartes