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geometry 几何 a solid figure with ends that are parallel (= the same distance apart at every point) and of the same size and shape, and with sides whose opposite edges are equal and parallel 棱柱体；棱柱 
a clear glass or plastic object, often with ends in the shape of a triangle, which separates light that passes through it into the colours of the rainbow 棱镜；三棱镜
Word Originlate 16th cent.: via late Latin from Greek prisma ‘thing sawn’, from prizein ‘to saw’.