Any right line passing through the center of a figure or body, as a circle, conic section, sphere, cube, etc., and terminated by the opposite boundaries; a straight line which bisects a system of parallel chords drawn in a curve.
A diametral plane.
The length of a straight line through the center of an object from side to side; width; thickness; as, the diameter of a tree or rock.
The distance through the lower part of the shaft of a column, used as a standard measure for all parts of the order. See Module.
Chew on this: Human teeth can detect a grain of sand or grit 10 microns in diameter. A micron is 1/25,000 of an inch. If you shrank a Coke can until it was the diameter of a human hair, the letter O in the product name would be about 10 microns across. Mary Roach
There is a new way with very very tiny fiber optics, which give an enormous high resolution. There are many many thousand fibers, very very close together with a very small diameter. Lennart Nilsson
Small bodies, about half a micron in diameter, and later referred to under the name of 'mitochondria' were detected under the light microscope as early as 1894. Albert Claude
Carbon nanotubes are amazing because they're really good electrical conductors, yet they are only a few atoms in diameter. You can make transistors out of them in the same way you can with silicon. At Berkeley, we made the narrowest device anybody had ever made. It was basically a single molecule. Paul McEuen
Now, therefore, the Directors of the company are hereby ordered to see that precautions are taken to make travel on said railroad perfectly safe by using a screw with at least twenty-four inches diameter. Joshua A. Norton