Mdtryhht

When working in a 2D coordinate system you could say that X is the horizontal axis and Y is the vertical axis.

Extending this to 3D, is there a similar word for the Z axis?

^{(I'm aware of Width, Height and Depth, but obviously horizontal and vertical aren't synonymous to width and height, which is why I don't want to call the Z axis the depth axis.)}

I doubt there is such a co-hyponym (if we can call it like that) to horizontal and vertical. You'll need to use an alternative name.

If you imagine the 3 axes, then the Z would appear "on the same level" as the X one. Depending on which ones you consider, 2 of the 3 will appear as such and actually, they are.

If you look at the Wikipedia page for Cartesian Coordinate System, under the section Cartesian Space it says:

For 3D diagrams, the names "abscissa" and "ordinate" are rarely used for x and y, respectively. When they are, the z-coordinate is sometimes called the applicate.

Emphasis mine. It says they are rarely used, but I doubt there are many other alternative terms, other than Z-axis, depth, and so on; they're the most appropriate terms, if you're looking for something technical.

In aviation we use the terms longitudinal, lateral and normal (or vertical) for the three axes. See this description.

Note that these are fixed relative to the aircraft, not the earth.

Original

Perhaps it's time to coin a new term? Here are a few possibilities I came up with:

• Applicatal (derived from applicate)


• Depthical (derived from depth)


• Zedical (derived from Z)


• Fordinal (derived from forward)

Edit

Upon further research, it appears that in the realm of print media, they refer to the 3rd axis of linearity as "stacked". So you have horizontal, vertical, and stacked printing layouts. Here is a link to the best explanation I could find:

• http://www.elkriversystems.com/PrintedOutput.aspx

In hind sight, when making user interface layouts where the items move along the Z-axis (in a list), I have referred to them as being stacked. Given that this is in the context of programming, stacked may work for you if you're referencing the linearity of a layout.

Plain English words may not always suit specific technical usage.

As for variable names, you will have to drop the h-v concept and adopt the xyz nomenclature. Just remember in 3-D, the z-axis is the equivalent of the conventional 'vertical' (the entire 2-D x - y plane being the 'horizontal').

[see also my comment @OP]

In my 3D coding experiences, we have called it the z-axis and depth. As well as z-values and depth-values used to mean the same thing. And also we rarely used horizontal and vertical, we just called those x-axis and y-axis.

Both of these answers are somewhat rejected by your question, but this is the answer I give based on my experiences. Maybe if you described the context of your usage, it would help.