diameter
/daɪˈæmɪtə(r); daɪ`æmətɚ/ n
(length of a) straight line connecting the centre of a circle or sphere, or of the base of a cylinder, to two points on its sides 直径
the diameter of a tree-trunk 树干的直径
a lens that magnifies 20 diameters, ie makes an object look 20 times longer, wider, etc than it is 放大20倍的透镜. =>App 5 见附录5. =>illus at circle 见circle之插图.