What Is The Difference Between Between A Solid And A Prism?

A prism is a solid that has two congruent parallel bases that are
  polygons. The polygons form the bases of the prism and the
length
  of the edge joining the two bases is called the height.

In a rectangular solid, the length, width and height may be of
  different lengths but all lines meet at 90 degree angles.

A rectangular solid is a prism but only a special case of prism is a rectangular solid.

Source
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