Solids with the same volume.
Example
A cube with an edge length of 5 cm is equivalent to a prism whose dimensions are 4 cm, 5 cm and 6.25 cm.
In fact : 5 × 5 × 5 = 125 and 4 × 5 × 6,25 = 125.
The two solids have the same volume; therefore, they are equivalent.