A straight line segment passing through the center of a figure, especially of a circle or sphere, and terminating at the periphery.
The length of such a segment.
Thickness or width.
A unit for measuring the magnifying power of a microscope lens or telescope, equal to the number of times an object's linear dimensions are apparently increased.
[Middle English diametre, from Old French, from Latin diametrus, from Greek diametros (grammē), diagonal (line) : dia-, dia- + metron, measure; see mē-2 in Indo-European roots.] di·am'e·tral (-trəl) adj.
(dī-ām'ĭ-tər) 