caliber vs diameter

caliber and diameter both are nouns.

Word	Noun	Adjective	Verb	Adverb
caliber	Yes	No	No	No
diameter	Yes	No	No	No

As nouns, diameter is a hypernym of caliber; that is, diameter is a word with a broader meaning than caliber:

caliber: diameter of a tube or gun barrel
diameter: the length of a straight line passing through the center of a circle and connecting two points on the circumference

Other hypernyms of caliber include diam.

caliber (noun)	diameter (noun)
a degree or grade of excellence or worth	the length of a straight line passing through the center of a circle and connecting two points on the circumference
diameter of a tube or gun barrel	a straight line connecting the center of a circle with two points on its perimeter (or the center of a sphere with two points on its surface)