prism
/ˈprɪzəm; `prɪzəm/ n
1 solid geometric shape with ends that are parallel and of the same size and shape, and with sides that are parallelograms 棱柱（体）.
2 transparent object of this shape, usu triangular and made of glass, which breaks up ordinary light into the colours of the rainbow 棱柱体透明物; （通常指）棱镜, 三棱镜. =>illus at spectrum 见 spectrum 插图.