Horizontal, vertical, and what?

Question

So there's a word for the x axis, horizontal. A word for y axis, vertical. But what's the word for z axis? I considered usining internal but then there's also external. Internal and external are the just words to represent values from zero, positive and negative. What is or should be a word for the third spatial dimension? Should it not end in al?

Answer 1

the 3 D axis? 3rd spatial dimension?

x and y axes are for length & width. z for height or altitude. altitudal dimension?