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.
e.g. ...a tube less than a fifth of the diameter of a human hair.
直径不足人的头发直径1/5的电子管
e.g. ...a length of 22-mm diameter steel pipe.
一段直径为 22 毫米的钢管