A line a thing is measured or turned about. An axis is chosen, and choosing it decides what can be compared.

Opened out to show what was folded away. The contents were always there; the state changed.

Of small extent across. Narrowness concentrates and excludes in the same motion.

Longer than its frame, so a view can be moved across it. Of a thing whose whole cannot be seen at once.

The vertical axis by convention. A named direction rather than a thing.