名词

1. 直径;对径
The diameter of a round object is the length of a straight line that can be drawn across it, passing through the middle of it.

1. the length of a straight line passing through the center of a circle and connecting two points on the circumference

Synonym: diam

2. 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)